You will lose money on it if you hire someone to do the work.
It is possible to make a bit of money if you do the work yourself. The cost of bathroom renovating depends on the size of the bathroom, materials, workmanships, and if the supporting walls/beams have to be modify or not. However, it is not worth the aggravation.
Post a floor plan of your current bathroom, and areas that may be affected by the modification. Also, post a floor plan of what you want to achieve. Are the wiring need relocation or addition wirings for lights & exhaust? Do you need to move door/windows? Is the door opening large enough to allow the bathtub to be move in freely or not?
The cheapest that will cost with no physical changes to the bathroom or fixtures except for adding only the tub will cost between $1000~1500 for materials (tub/shower surround + flooring + paint). However, most bathroom renovating start well over $5000 for a small bathroom with labors.
A realistic cost with labors would be at least $10000 for materials and labors.