As far as HML's go, they will double check your deal to make sure the numbers work (for both of you) as they are not going to lend on a property that they have not vetted. 

Would doing this basically double the lender fees since I would essentially be taking out two mortgages? 

In general you can't double dip and charge the old departing tenant while alos collecting rent for the same unit from a new tenant.

Most prices doubled (some tripled). 

Have you asked them to double flush (i.e. flush early and often)?  

That being said I purchased a beer water meter back in May 2019 prior to that I was making 1 to 2 deals every other month with Wholesale in assignment contracts double clothes and what have you.

You could gather all of the information from the internet but double checking with PM's would be smart as we had multiple changes in May as you know. 

Maybe it cost double that amount?

An older property with low interest rate and into cap-x can easily do much more poorly than a newer unit with double or even triple the interest rate but limited or no cap-x. 

Right now, a reasonable estimate is a low double-digits interest rate (say 11%-14% for example) with a few origination points (say 2%-3% for example).