Some more consolidated thoughts....
1) You will want to(if not be required to) own the land outright before approaching for a construction loan. The land will likely be somewhere in the 10%-20% of your homes total value. This is your required equity in being approved to move forward with the construction loans.
2) Construction loans. You'll have to shop around. Banks vs. credit unions...vs bank vs bank vs CU vs CU...they all have different equity requirements, payout methods, interest rates, "gotchas" to cover. Some places will require you to have 80% equity (if you have a $200,000 home contract, you'll need $40,00 in equity/downpayment). Others are only 90%. So on that $200,000 home you'll need $20,000 down.
The construction loan is a temporary loan that intially will cost you very little, and then will continue to increase as more draws are made on it. It's based on a 30 year amortization and will have a higher rate than a mortgage.
For example:
1st draw will come after the foundation is in. Say, $40,000 for excavation and pour/blocking of foundation and rough in plumbing of basement. So you'll be paying like $200 a month until the next pull. That will come after framing, which is around 1/3 of your total contract price. So if it's a $200,000 home you are talking around another $60,000. Now you have a construction loan of around $100,000 you are paying on. Now you are around $500 a month.
You might have a 3rd pull after the electrical, plumbing, and drywall is in, taking your loan up to $150,000 and then a final pull happens when you sign off and roll into a conventional loan.
3) Costs to consider. You say you want to build in the country. Fine. You have to consider the costs of doing so. You'll be likely on a well, will be on septic, and will have to figure out if natural gas is available and how close the electrical run is. A well is going to run you anywhere from $5,000 for a shallow well to over $25,000 or more if you have to drill deep. Septic is going to run you between $5,000 and $8,000. If electric is not near you are looking at several thousand, if not tens of thousands of dollars to have it trenched and terminated at your lot. Then you have other considerations like trees, access, drainage, and elevations to figure out before putting house on the lot. You could easily have $100,000 invested before the hole for the house is even dug.
4) Builders/GM's.
There's three main types of builders.
1 - They show you a plan and build what they want. Very little customizing outside of carpet, flooring, cabinet and paint colors.
2 - Semi-custom. They have a set of plans that they like to work off of and will let you tweak room sizes, give you control over most things like siding, flooring, fixtures, window styles and sizes, ceiling height, door styles, ect.
3 - Full custom. They will build you a home exactly as you want, even if it's a disaster.
Sweet spot is a competent builder in the 2nd option. That's what we did. There were simply a lot of things that I didn't know what I wanted or how I wanted and I deferred to the framers/general on what to do. They had built over 800 houses...I was on my first. I simply didn't know what was appropriate in some situations. Most of the time I was very happy with their suggestions. There's a few I would do over again having lived in the house.
5) General suggestions....go shopping. Hit up open houses, house parades, ect. Look through houses and understand what is important to you. Do your homework and figure out what that type of setup is going to cost you. Cabinets, counters, flooring, ect. All of that adds up. Same with kitchen layouts and bath rooms.
Speaking of bathrooms, unless you or your wife are big bath people, just skip it in the master and put in a huge walk in shower with heads on both sides of the stall. Put in a bench that you can sit on and just relax and enjoy the warmth. That's what I wish I had done. Instead I've got a huge, jetted corner tub that's been used exactly three times in 2.5 years.
Garages - GO BIG. Most builders have like 2' of space between the outter edge of the garage door and the wall. So if you have a car with big car doors you barely have room to open them. Cars have gotten A LOT wider over the years but garage doors haven't. Make your garage *at least* 30 feet deep and give yourself a good 5' of room to each side of a car door. That leaves plenty of space for cars, a few utility shelfs, and your mower and other stuff.
Heating/AC/Insulation. Pay good money now and build it right. I've got a 2x6 studded house, with a ridgid foam wrapping, and enough spray foam to float the titanic. My energy bills are about what a typical house half my sq/ft would be. And that's just with conventional forced air heating/cooling. It would have taken me a long time to recapture the investment on geothermal, if ever. I'm still not *entirely* sold on the tech.
What I would do in a future house though is this...it'll be a large ranch with a 10'+ tall basement that was fully finished. Both basement and main floor would be heated via radiant heat and zoned. If I was in a cold/snow area I'd also go radiant heat in my garage and also do a snow melt inslab setup for my drive way. If you do radiant heat and a primary heater tank to feed your radiant system you would have a very efficient, comfortable setup. If you are expecting snow, you turn on the manifold for the driveway and get it going and never have to lift a shovel. Awesome. Not cheap. But damn nice.
6) Other other things....
Just know what you are getting into. This a year plus long commitment that is incredibly fun, but also incredibly stressful. Know your contractor. Get feed back from prior customers. See how well their place has held up. How easy the GC was to work with. Ect. You'll be talking to this guy multiple times a day for the next year or more.
Don't just plan, *EXPECT* overages. At least 10%, if not 20% more. And that will likely have to be paid in cash at the end. Your construction loan is only approved for a certain amount of money. Going back and re-writing that is very difficult. If you are at the end of the build and your contract/appraisal only accounted for basic porcelain tile @ $2 sq/ft and modest cabinet configuration for $5,000......but your wife now wants a luxury tile pattern that is $9 a sq/ft and a fully framed custom cabinet set for $25,000 that money has to come from somewhere. You can talk to the bank about rolling it into the conventional at the end and cutting the builder the difference back in a seperate check...or you pay it in cash. Regardless, just know that you will go over. Something always comes up. There's something here or there that you want to upgrade. A room that you want to tweak. A wall you want longer. Ect.
Just do your homework on everything. Shop around on quotes. Get feedback from past clients. And figure out what you want, vs what you need and meet somewhere in the middle.
I just hope that you and your wife have similar tastes in things and have the ability to compromise on some areas. It's going to have to happen to make a build successful. Unless you are made of money there are always compromises that will have to happen. Make sure that you are fair to each other. This is where many of the arguments come into play. All disputes that a couple can have are distilled down into a single focal point over the course of a year. Money being the number one. Control and concessions being the second. General stress and anxiety being the third.
Take your time, understand your financial limits, and see if it's practical for your young family. And be sure that what you do down makes sense for your family 5 years from now. Maybe even 10 or more years from now.