I could see how they might be entitled to a percentage (same as with the rent) for the extra time to follow up on the late rent, but then again part of their job is to collect the rent and most of the time, if they've done a good job screening, that should be a piece of cake. 

And maybe pay off debt first if those percentages were reversed. 

That's purely an investor only, no equity stake.Offer a lesser percentage, but a percentage equity stake on any refinance or sale on the back end.Go 50/50 partnership and they bring the cash you bring the deal.

The single best point buy I saw was a 1/4 percentage point rate decrease for a full point. 

Should the adjustment be based on any index or be a fixed number/percentage?

If I decide to buy a property in Maryland, does anyone know of any areas with a high percentage of renters ?

Yes the lender could call the note cause you transferred the property, but that is a very small percentage possibility.  

I know there are a lot of lenders who charge only a flat fee/origination percentage basically to keep their lights on but everything else comes from the title company. 

Whenever I buy a note (usually non-performing) it has to have plenty of equity on the loan to value as well as a percentage of loan balance.

As for refinancing, a good rule of thumb is that if you can get a whole percentage point lower, go ahead and save yourself the money, but for anything less than that, what you save in interest may be outweighed by what you pay in loan fees.