@William ThanI suggest speaking to local banks and credit unions.

They require a higher credit score and private mortgage insurance if the down payment is less than 20%. 5% down payment loans cannot be used for a 5-unit property.

The background check didn't show anything concerning but the credit check showed a credit score of 523.

What documents do they require, what credit scores do they allow, how do they verify previous rental history, etc.?

What Is your FICO score?

By signing below, applicant(s) give permission to (1) current and former employers to release any information about applicants’ employment history and income history to the above named person;(2) current and former landlords to release any information about applicants’ rental history to the above named person; (3) current and former mortgage lenders on property that applicants’ own or have owned to release any information about mortgage payment history to the above named person; (4) bank, savings and loan, or credit union to provide a verification of funds that applicants’ have on deposit to the above named person, and (5) to the above named person to obtain a copy of applicants’ consumer report (credit report) from any consumer reporting agency and to obtain criminal background information about applicants.

Monthly joint income is 7X the rent and one credit score is 630 another person is: 712.

If your credit score is above 700 and you can show a reasonable W2 or 1099 income they are not hard to get approved.

Got $100k business line of credit with 710 credit score to buy some more properties.Do you think it is better idea to buy a rental house (worth $70k) with the credit card paying all?

Once you take it out, you stop banking with your normal bank or credit union and you now redirect all your income / deposits into the HELOC.