10% is a reasonable amount to put down.
I second the merits of the 80/10/10 loan.
80% - Main mortgage
10% - Down payment
10% - Line of credit, or 2nd mortgage, or outright loan
I have one of those, and I don't pay PMI - but I do pay $75 a month for my extra "10%" line of credit. That is the interest-only payment, IE I will never pay off that loan at $75 a month. However, that compares favorably to PMI (which was looking like $150-$200 a month, for 2 years minimum) and the $75 a month is tax deducatable, which means it's really only about $50 a month at the end of the year.
You really have to sit down with a notepad and a calculator and do lots of "what ifs" on paper to see how the #s compare for down payment, monthly payments, etc, and how they compare based on how long you think you'll be living in the house.
Edit: It does seem kind of odd that you'd be looking at a house when you're here on a work visa. Think hard about that - because if you're only here for 4 more years you're probably right at the edge of making it worthwhile to buy, unless you happen to get lucky and buy in an area *Before* it starts to appreciate, and happen to own it through a stretch of increasing prices. Everyone says "oh you're throwing your money away on rent" but they are full of BS. That's what uninformed people say to justify their home purchase. Here is how it looked for me:
$920 a month rent included water, and my electric bills were about $80 a month (apartments will almost always save energy, since your neighbors will offset some of your heating/cooling $)
Now I pay:
$950 a month 1st mortgage (this is the # that the loan calculators give you.. they don't mention the info below)
- PLUS -
$75 a month line of credit (my 2nd 10%)
$50 a month water/sewage
$100 a month insurance (required)
$40 a month more on my electric bill (~$120 total)
$200 a month TAXES
So the way I see it, I am "throwing away" $465 a month right now, that I wasn't "throwing away" before. Now some of that will be offset by tax breaks, but I'm not 100% sure how much yet.
Now it's all good if my house happens to appreciate... but at the same time, $465 put into the bank every month would be $22,000 at the end of 4 years. Will my house appreciate $22,000??? Guess I'll have to wait and see.