I'm not even criticizing them.

It worked fine for basics, and I even did some barely passable permit drawings on it, but it is by no means pro-quality.  

The MIRR formula works even better because the cash flow from the rental property is not automatically reinvested into the property.I think that building a spreadsheet with both scenarios, stocks, and rental property would answer this question.

Its not even the risk of getting sued, most platforms (that are legit and operate in the US) won't even authorize your campaign if it looks scammy or that you don't have consent.

As Lindsey mentioned a lease is important and sometimes even a small security deposit.

While property appreciation may be lower compared to other areas, the cap rates often exceed 10%-15%, even factoring in mortgage expenses.

Even if you get a solid PM I always like to double-check the county court records and see if anything was missed. 

You may be even selling some of these smaller assets and roll the equity into the bigger dealsThese small deals can make an investor incredibly wealthy, especially if the equity is owned by a few investors.

In the eyes of the law, any legal conflict between you and your guest will be treated as a landlord / tenant conflict even if the rental is a room in your own home.  

Even more reason to not worry about it.