Gotta agree with Kerry on this one.

Having a 21-yo take on a 150k mortgage is an iffy proposition. You need to have everything clear and in writing. Is your mom going to stay there? What happens if you default? Are reverse mortgages not an option? Is the house worth what your mom wants? Is it an asset/liability you really want to take on?

IIRC, you're either active duty, guard or vet. Are you using VA or some other program? They may have special rules or inspection requirements. Or they may have special rates. Don't overlook them. If you have the option, contact your JA.

Maybe an estate planner or local real estate attorney is your best bet.

Since you asked about special circumstances, there are some listed here:
http://www.bankrate.com/finance/real-estate/7-tips-for-selling-your-home-to-family.aspx