The lender paid $70k, and only asks for $750 per month. 

Let's say you paid $250k for it, and it's now market value $500k.

The loan is still on my name, but is being paid off every month by my buyer.

.: I just added up all my interest paid in 2024.

I’m trying to figure the best way to structure the deal (equity, yearly dividends on cash flow, etc).

Don't be so quick to indebt your paid off townhome until your learn creative financing and review all your options.

Current value of paid off property is roughly 350k , looking to borrow 75k-100k down payment to  purchase a 275k commercial property.

The tenant has not paid anything since April 2024, effectively staying in my property for free for four months.

If you had $50K in a Self direct IRA how would you leverage that to yield short and long term dividends? 

This should be able to be linked to a holding outside of Spain to transfer e.g. dividends, however, keep in mind that other countries will ask you to have substance there for them to approve the holding.