Or split my earnings with them?

I used a hard money loan to purchase this off market deal.I rehabbed the upper two units within two and a half weeks and have a renter already lined up for one unit.

To start you need money, Your money or someone elses.

I am proficient in investing and confident in earning 7-10% returns in the market over the next decade or two.

I have around $100K in liquid capital and access to a $50K HELOC at 6% for the next 10 months before it transitions to a variable rate.I have a unique situation where I earn a living through sports betting, which limits my ability to show traditional income growth.

You use $50k of the loan to do the repairs.If you have 20% down + rehab money, then you can do a FNMA HomeStyle program.The FHA 203(k) is a great BRRR tool. 

second was Hard money it was legal then. 

tough one.. generally you have a captain and then crew.where I have seen this work is through an earn in situation.

You have to "earn" those returns either way, whether investing directly or giving your money to a syndicator. 

If I believe I can generate enough profit this year and navigate any potential inspections next year, I’d be comfortable moving forward—using the income earned to cover any necessary upgrades.An alternative exit strategy is to document the financial performance and sell the property as-is, highlighting its strong short-term rental income.Think through your next five moves, from best to worst-case scenarios, and make a decision that aligns with your goals.