Also, in order to get financing the lender wouldn’t allow SCI to dramatically overpay or they wouldn’t meet the debt service requirements.

My question again stems around using seller financing to allow them to receive a consistent monthly pay of X amount and delay/lower their tax bill in the short term instead of going through a lender to borrow 800k+ causing my mortgage to be significant part of our income roughly 40-50% of take home -  which we are approved for LOL.

Other than paying for an appraisal or BPO (and maybe a credit report), you should not pay a lender anything until your loan funds.

Maybe a mortgage lender can chime in.

We are coming down to get a feel for some neighborhoods we've been looking at moving too and don't really have too much planned so I thought it would be a great time to connect with some lenders, investors, contractors, and liked mind individuals while I'm there!

Are there specific lenders or servicers that are more likely to call these loans?

Then if/when another good deal comes up, you can approach a lender and look at leveraging either of the properties in order to fund the down payment of the new property.

I would get the same deal if I did another with the same lender. 

That would be for the deed, so use care not to trigger the acceleration clause with your lender.

I have a robust team of mortgage lenders, title companies and RE attorneys.