Bill,
There are a few different sources to look at. But, at the moment, Bill Bronchik comes to mind.
His articles are posted here and there is also more on his own website.
Here are the addresses.
Need some help. I’m looking for a good article on acquiring title to a property “subject to” the existing financing even though the mortgage isn’t assumable. If you don’t know of a good article, but have had experience handling such transactions, I would appreciate your personal “how to”.