There is a difference between "best" and "lower cost". 

Crexli and Loopnet are expensive but useful for research purposes.What do you recommend?

If you're just looking to lower your payment, then take the total costs its going to take to refinance (at the very least 5k) and then divide that by the monthly cash flow improvement you'll have by getting lower rates.

There's a fair chance that you are going to have to lower your rent beyond your normal rate or expectations. 

Rather than perform tests to make life more expensive these simple steps will cure most issues.

transacting - buying and selling - is expensive and can consume years of gains, with all of the commissions and fees you have to pay. 

It will almost definitely be more expensive and take longer than you anticipate, and those HMLs aren't cheap. 

I am in the process of doing a foreclosure in SC right now and it is long and pretty expensive (this was a NPL I purchased).  

Lower of cost or market for determining the basis is also the correct way to treat a personal use asset being placed into service for business purposes.

I used RLS back in 2018, when they were still ascending in their fame and riches, and not yet so expensive.