What is the return on investment? 

If you go self-employed, youll need two years tax returns.

Frankly owning 30 properties in 30 different LLC's would be a migraine come tax time to get returns prepped.

If your bottom line numbers on tax returns and W2 income are not strong however, this will be an abrupt dead end.

Just make sure everything is updated and you will be able to manage it easily.

I think a return on invested equity analysis outlining a few scenarios with my models would answer your questions. 

If they are professional, they can explain this quickly and easily.

Since you're not looking to make it a full-time career, you might consider passive investment options such as investing in real estate syndications - this GP/LP structure as a limited partner, allowing the GP to earn you a return allows you to invest in real estate without the day-to-day responsibilities.

But I would think they all can easily run the comps so you know the numbers you are aiming for in any given neighborhood/block/property. 

will you have a net positive return vs selling it as a 4 unit?