For the purposes of this venture, I have about $80k that I will bring to the table.

Absorbent materials (paper, doilies, whatever) on all hard furniture surfaces like desks and tables. 

@Drew Wa depending on the tenor of the installment sale, IRS does have a minimum interest requirement - ie. if you claim a 0% interest rate, the IRS has a table with what the minimum interest rate should be on an installment sale of that tenor, and you will be paying taxes on the deemed interest.On the capital gains front, I am not 100% certain, but it would make sense that any installment gains received in the first 12 months of your purchase of the property would count as short term gains and anything after 12 months would be long term, again, not certain as to this point.

Bring something to the table, be upfront, and find a someone doing the same thing.   

If you have experience and the deal they you essentially bring a bit more to the table.

Option 1 is really on the table because you're saying they're on good terms and can just, in writing, confirm that they've vacated.

Who do I need at the table in order to realign the titles?

Everybody wants a piece of the pie, but not everyone is willing to do what it takes to make it to the table.

Found it on Redfin, made a low offer but accompanied it with an emotional appeal letter which helped “keep us at the table” finally agreed on a price.

I am thinking I would rather take the equity,  BRRRR, and house hack, but I am leaving all options on the table.