I like to make more reasonable offers and negotiate credits during the inspection phase. 

The landlord-tenant relationship is simply not all about bloodless logic and the simple exchange of money for a service or product.

Then, decide on the product: SFHs, small MF, large MF, office, retail, etc? 

. , If you take the money out of the equity line of credit ( it is not called HELOC if it is not your home), there are few treatments. 1) If you invest the money taken out in the investment or other business, the interest is deductible in that business activity, not at you rental activity. 

I bought & rehabbed a house from 1000 miles away using my personal credit line.

You need to find a broker or banker that has these kinds of products.

You want clients that have credit issues.

I thought I could sell it to the renter but they have no credit.

I have a great credit score (above 800) and solid assets and I would pay far more for money than a conventional loan rate if I were getting money for any investment other than one that qualifies for a conventional home loan.If ROI is your goal then the implied goal is to leverage your money for its greatest return. 

Borrow from family, use credit cards, sell some assets, save.