The lists we pull are primarily LLCs, and Skip Genie, my go-to, does not skip trace LLCs.

At this stage in the game I'd say as a general rule skip the mentorships and gurus. 

Nor any skip trace agency who will guarantee correct address. (7) We have not been able to find any collection agencies that take case of a private landlord to collect on contingency basis.

They use a credit system where they give free skip tracing for 250 numbers+250 emails+250 email sends (which is nothing) then you are paying .08c for 1 number or email or address.

While you may always have a skip, early termination, or eviction, spreading out the lease-end dates can help avoid having all units vacant at once.

Start mailing and skip tracing some small multi-family properties and keep at it.

So, if the tenant doesn't pay, skips out after damaging the property, and it stays vacant for two months it's OK because you don't owe anything on it.

Quote from @Robert Ruschak: Would you skip the 700+ single family houses and scale up faster into multi-family?

A more intrusive approach would be to Google the owner name and see if you can find relatives and skip trace and call them.

Also, what skip tracing service are you using to find owners number.