How to Assume a Seller's Mortgage?

Hi Everyone,

I was referred to a potential private sale of a multi-family through a friend.  My business partner and I aren't 100% sure we will qualify for the conventional financing we have used on our previous deals due to both of us recently leaving our W-2 jobs.  (I've posted about this conundrum elsewhere if you want to weigh in!)

Anyway, one thought I have is, since it's a friend of a friend, maybe he would let us assume his mortgage.  We probably have the case to pay out his equity piece of the purchase price.  

I am wondering how this works, practically, however.  I assume mortgage companies will not agree to such an assignment?  Is there a work-around?

Many thanks!

Jeff