The safest way to create what you're seeking is generally to own fewer units, manage them very well, and de-lever them. 

Nothing could be more dangerous and she should understand the risks of this.If I were your friend, I would also want to know how you will pay me back.

If it's a seller's market, you will typically find fewer sellers willing to seller finance.

You are walking a very dangerous tightrope with advocating mortgage fraud. 

Even if I don’t pull out all of my cash invested, it should leave me with less out of pocket and a fixed up property with fewer issues moving forward.

The opportunities are fewer for bigger properties but it’s less hamster in a wheel than trying to get 20 SFHs.

Not to say they don't exist, but there are a lot fewer and your large banks won't if you own in LLC.If you go with cash, just understand your cash will be tied up in the property for at least 6-12 months, until you reach the seasoning for your lender to refi on new value.

@Richard Hayes also keep in mind the dangers of having money and little investment experience.

Depending on your exit strategy for the property(s), you may have more or fewer buyers competing when you go to sell. 2.

There is some offset that there are fewer "lookers" and more of those few are active "buyers."