Not a lot of our competitors offer this but it's something we can consider (but for us, it can't be in a rural area, the loan amount must exceed $150k, if we're using PadSplit income (or STR/MTR income) the max LTV is 75% and the down payment must come from your own funds). 

Have proof on hand (easy enough to find) online of the missed tax payments and any documentation that supports that he specifically didn't pay his taxes.Probably a simply mistake on his part, but now if he wants to develop on it, he either has to land lease it from you or buy it back.I'm not sure how the whole tax deed thing works, so that would be something you have to figure out between the two of you.

I was thinking I could put down the 50k so he had enough to pay off the heloc and make payments to him for the remainder to be paid off in 10 years with new renters.

That’s an incredible deal—congratulations on securing 100% seller financing!

I would just take into account that a lower down payment will mean a higher monthly payment so be sure to run the numbers conservatively in order to ensure your STR revenue is able to carry your monthly payment with this higher mortgage cost. 

Principal buy down that occurs with each payment met.3.

I've wondered that myself and thought: If an investor was looking for birddogs why would the birddog have to pay the investor money before they began securing leads for the investor, that the investor would then in turn give the birddog an investor's cut on the profit end???

.- Financing: Starting with cash but hoping to secure loans for future investments.

I then modify those numbers based on the buyer's preferred down payment/return hurdles.

Short of selling my entire portfolio, the liquid capital for the down-payment remains unattainable.