When you can borrow 80% tax free and continue to collect the income?

Unlike CPAs, EAs focus on tax matters and can represent clients before the IRS in audits, collections, and appeals.

Do they offer to help you collect or file a claim against them?

My question is: On new loans-how can we collect from each investor a small fee for our monthly services. 

It does many things to help you with Tenant placement like marketing, application collection and screening. 

I do not recommend paying any upfront fees, unless it's with a large bank that typically requires a good faith deposit on larger transactions.

Many opt for other investing methods in their SDIRA like private lending, crypto, private equity...anything except collectibles and life insurance.Note that a Solo 401k is exempt from UBIT on leveraged real estate so if you have self employment activity and no full time employees save for you and your spouse you should consider the Solo K as an option. 

Also, focus on 2 years of job/income stability.Class D Properties:Cashflow vs Appreciation: Typically, all cashflow with little, maybe even negative, relative rent & value appreciationVacancy Est: 20%+ should be used to cover nonpayment, evictions & damages.Tenant Pool: majority will have FICO scores under 560 (almost 30% probability of default), little to no good tradelines, lots of collections & chargeoffs, recent evictions.

We never collected any money for rent from anyone. 

Also, focus on 2 years of job/income stability.Class D Properties:Cashflow vs Appreciation: Typically, all cashflow with little, maybe even negative, relative rent & value appreciationVacancy Est: 20%+ should be used to cover nonpayment, evictions & damages.Tenant Pool: majority will have FICO scores under 560 (almost 30% probability of default), little to no good tradelines, lots of collections & chargeoffs, recent evictions.