HELOCs are not available because they are residential loans guaranteed by individuals and what you seek is a type of commercial loan or credit line which are available to seasoned companies with proven financial track record.

You're using a company to manage tenant phone calls/inquiries and then send in vendors for repairs.

My company provides a comprehensive A-to-Z solution tailored to our clients' needs.

Many skip tracing companies have a minimum count or spend.

The companies that market themselves as "garage door companies" (residential) also almost always do commercial stuff as well, such as what you are looking at.

Some companies allow property owners to select tenants and set the screening criteria...We do not - our criteria does not bend. 

Or does one need a special license / need to open a company?   

There's more low-hanging fruit here than I'll ever need, but hitting the ground running to pick it before land prices start reflecting the new higher values requires more capital than I have and I don't do debt.There are two main companies in the US who do the work of creating and selling eco-mitigation credits on a joint venture basis, separated by the Mississippi river.

What other company offers business income loss and up to 15k for dealing with squatters?

Find information on transfers is kids play for any of these companies.