Here's a list of things to track:- Formal lease application- Formal signed and executed lease specific to your state- Payment history (I recommend using online rent collection like Apartments.com, RentRedi, etc)- Maintenance requests and receipts- Accounting for all rental-related expenses (repairs, utilities, etc) The more you treat it like a business, the more helpful you are to your CPA come tax time. 

Do you recommend switching at around 30 properties or so? 

I highly recommend you work with agents in the future.

@Scott Isbister @Tony CanevaroLike Scott I do recommend the collaborate real estate meetups as well.

I don't personally have an umbrella policy but if you do want to be extra safe, yes, I would recommend an LLC and umbrella policy together. 

Did you work with any real estate professionals (agents, lenders, etc.) that you'd recommend to others?

Honestly looking at your situation I'm not sure I would recommend you do the taxes yourself,  change of accounting method (F 3115) isn't easy for someone that hadn't done them before these online software companies make things seem easier than what they are, they are good for less complex situations. 

I do recommend creating (and keeping updated) written policies for all of your leasing and screening process, and making them available to folks during the application and screening process (talking about, sending links to, emailing, & reminding, the more times they see it the better even though they likely won't read it).

@Sami Gren I would not recommend accepting rent through a random App that you did not set up yourself.

A special committee was formed last year, and was to hold 6 non-public meetings and then send their finalized recommendations to the commissioners in November.