I have an existing townhome mortgage subject to renewal on Feb 2016. Can my son assume the mortgage should we sell the house to him?

Read your loan documents. It will say in there if the loan is assumable or not.

Assumable Mortgages are far from over in the US. In fact, ALL FHA and VA mortgages are assumable in the US as long as the potential buyer qualifies under the respective authorities creditworthiness standards.

If the mortgage is FHA or VA then yes it is assumable, and as long as your son can qualify he will be able to take over the mortgage upon purchase of the home

Only reading the boilerplate in the mortgage can tell you if it assumable. I can tell you from looking at a few thousand mortgage documents a year virtually none are assumable.

A brief phone call to your lender should settle the question for certain.

Probably not. Your son will be required to obtain his own financing. The days of assumable mortgages are just about over.

BE CAREFUL that you sell him the house for fair market value or you will run afoul of IRS rules regarding gifts (or file the appropriate gift tax forms).

You can only do so IF your mortgage loan is assumable. If not, then your son will need to obtain his own mortgage loan in the conventional fashion.

Almost all mortgages in the US are not assumable. You would have to ask your mortgage holder.