Start small, be patient, and stay connected with local meetups and online investor communities for support. 

Small demolition projects make massive impacts.

It’s also helpful to build a small network of trusted vendors and tradespeople you can rely on for future projects.The BRRRR strategy can be a great way to scale, but I’d advise budgeting some extra cushion for unexpected costs or delays—it’s almost inevitable.

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

If I were to approach a seller of a $200k home, and they had a remaining mortgage of $100k, could I get a new bank financed loan for that $100k, and have the seller finance the remaining $100k of equity to me?   

Wouldn't you rather be a big fish in a small pond?

I am small time but haven't ever  had a disaster experience with pets.

And you have to pay PMI for the life of the loan.

If the other two parties want to flip a house maybe they can do just that as partners and then sell you the house which you can buy with a primary home loan with low down payment.

While you work on that, you could also explore creative financing options like DSCR loans or partnerships to fast-track your first STR.