You can use DSCR programs that only looks at your credit and the property itself.Either way, it will be important to have a high enough credit and down payment to qualify.

In theory we could buy a house with him and rent it for ten years and break even, pay the debt down, build credit, and later maybe he lives there.

I see they suggest offering the tenants the option of paying by Credit Card.

I usually suggest new property owners setup a business before they even close on a property and then use a business credit card for all expenses moving forward and also for them to link it to Quickbooks so everything is automatically tracked for them.There are a lot of nuances and strategies but this is a 30,000 foot view of why you should opt for business>personal

If you are using a local credit union or balance sheet lender they have additional qualification standards but I see you are in Oxnard.

Lets say the investor didn't use credit or anything related to credit metrics to buy the property (maybe own cash, OPM or HL, by the time the "refinance" part kicks is, what happens if the owner has credit issues and the financial institution won't proceed?

Low taxes and regulations. 

Make sure your financial situation is stable, with a strong down payment, an excellent credit score, and a clear grasp of your budget and objectives.

When you reach the age of 19, it's important to have a reliable source of income, be able to provide a down payment of around 15% to 20%, and maintain a good credit score and debt-to-income ratio in order to be eligible for a mortgage loan.

Depending on the loan amount, LTV, your FICO, length of PPP, etc I'd guess that you'd end up in the high 7s - low/mid 8s for a 3-unit property.