For example, we've recently taken over marketing internally because the property management company was not experienced enough in using the newer advertising methods we need to pursue.

You can create your own methods and one stop shop by creating your own leads.

Now, it’s time to explore the various methods of investing.

I take a methodical and pragmatic work approach. 

Whomever will do her taxes when she does sell, (can be done prior, and should be asap) will have to submit a change of accounting method form .....I've had multiple clients that never took depreciation and when they sold, we had to fix it...doing your own taxes isn't as easy as some tax software companies make it seem 

If I had a bunch of houses and hired a plumber to fix a leak in the first house and he “fixed it” then six months his method fails.

Obviously the numbers and location would determine which is the best option for me but these would be my preferred methods. 

Since you aren't looking at the BRRR method, I am assuming you want something that is turnkey.

Some have used this method to obtain 100% financing.

Definitely do more research on the BRRRR method as that sounds like what you're trying to do.