Assumable Loans to obtain past interest rates.

[Chase Olson]

Does anyone have experience in assuming someone else's mortgage for a fee? I'm looking at buying a SFH that had a refinance back in 2020, so I am assuming the interest rates on the mortgage are lower than they would be to create a new mortgage today.

I figure I could pay the sellers a lump sum and if the mortgage is assumable, go through the process with the lender to have the mortgage transferred to myself. 

Is there a certain way I might make this more enticing to the sellers? there wouldn't be any originating fees or closing fees I imagine.

or am I completely wrong and the lender would bring the interest  up to market rates?