They've been a client for over 3 years, I've watched them flip 300 properties, and they started with very little real estate background.

Your background in Engineering should help you be a good leader.Being interested in buying rental units is one of the best ways to go.  

I do not have any background in real estate.

I have a background in construction and have worked in contracting for many years.

If by the time you complete a background check, credit check, employer verification, conversations with previous landlords, an application fee, deposit and personal interview you're still having problems with your tenants, you're doing something wrong.And if you're unsure about being a landlord in general, then you can either put people on month-to-month leases so you can quickly get rid of them, or hire a property management company to manage it for you.While the landlord laws may look great in some other states, you'll may also be missing out on all the fabulous appreciation that can be experienced here in California.

Some background info:unit 1: $1150/mo – upper unit with view, some recent renovations. on year-long lease ending 11/17.unit 2: $775/mo – upper unit with view. month-to-month, tenant since 9/10.unit 3: $800/mo – lower unit. month-to-month, tenant since 7/14.unit 4: $775/mo – lower unit. month-to-month, tenant since 5/11.unit 1 i'm happy with.unit 2 looks like the biggest opportunity for raising rent. in it's current condition, it looks like i could get 875-950 for it. after some updating, i could get 1100-1350 for it.units 3 and 4 could probably max out at 850. after improvements i could get ~1k/unit.if they are good tenants i would like them to stay. i certainly appreciate the longevity. any advice would be greatly appreciated.

There are a few pockets that resemble North Park with beautiful restored homes, owner occupied, etc.  

While most of the houses I buy can be considered ugly, to me... they're beautiful!

Starting to get my forms ready - renter application, etc  I want to have a system in place for this place and future investments.My question is what is the best background and credit report site?

I haven't got results from her background check or credit score yet.