I’ve bought some houses with 0% interest for a year credit cards and a few with consumer lines of credit from banks.

With your experience and possible skillset, perhaps finding a company to sponsor you for a green card may be a better option? 

What about Debit Cards attached to a checking account?

How affective are physical mail cards with deal machine?

I don't take credit cards but I believe stripe does.   

You want this to be your backup plan if things take longer than anticipated, you do not want to dip into personal credit cards so i would use a heloc to help with down payment but try to keep a nice available balance on a heloc as your insurance policy. 

Look at what high interest credit cards you can get rid of, pay down, or move to zero interest promotion cards for say 15 months etc.

I do direct booking through the Houfy website, taking credit card payment by Square. 

Once you’ve made all of the rookie mistakes and have your SOPs in order, you can go invest out of state with a game plan.

While you save up work on building up your credit history with a credit card.