We have in the past, although with rates as low as they still are assuming debt that was placed pre-covid is rarely accretive for two reasons.
1: Rates on assumable mortgages from pre 2020 are significantly higher than rates today, although that spread is narrowing on fixed rate debt indexed to the 10-year treasury.
2. Very low LTVs. The value spread between now and even 12 months ago is huge, a deal from a few years ago is even more. This results in a very low leverage deal, especially if the loan has been amortizing and w/o additional interest only.
You can sometimes get a mezzanine or a supplemental loan that is subordinate to the first mortgage, however the rates will be higher than the first mortgage.
The only reason to even consider an assumption in today's market is if there is a high pre-payment penalty that would make the sale free and clear unattractive to a seller.
If you don't mind very low leverage, and there is significant upside that can he harvested when the pre-payment is either phased out or the new value is so great that the pre-payment is in-material to your return.
Where assumptions might make more sense in the future is if rates rise significantly and deals with sub 3% debt come back on the market that are assumable, it might make a lot of sense to assume the current low rate loan and also take out a mezzanine facility to bring LTV closer to 70-75% range. In this case your blended rate could be lower than what you could achieve with a new loan.
Helping a seller avoid a pre-payment penalty may also make your offer more attractive, and even get you a slight discount. It's not uncommon to have a seller say "assume it and we'll drop the price by X" or "free and clear is the offer price plus the pre-payment."