Anyone you can recommend? 

For those who manage your properties out of state, what door locks would you recommend?

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. 

Buying quality assets that are in a desirable location and in good condition with a modest amount of leverage is IMO the only approach that I feel comfortable recommending.

I recommend continuing to learn pros and cons of each and determine which paths (I pluralize it as you should diversify even across real estate).

I highly recommend them! 

I recommend you start with duplexes as you should always have a paying tenant.

My sister doesn’t recommend buying warranties anymore.

Readers should seek professional advice.

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