Real estate investing is forgiving; the average person can still make money even with some big mistakes.

Our average tenant stays 12.5years.  

Although it also depends on your projected usage and average length of stay.

Average household income in Albuquerque is $83,000, with a median home price of approximately $365,000.

If you aren't doing it, you should use the average amount with the oil company based on other year's usage and they will average it so it's not $500 in one pop (depending how big these tanks are).

The average car is parked in each spot for 20-30 hours.

I would ask what their commission percentage is, how much training they provide, if they require you to be in the office, and how much their agents make on average. 

Ask key questions like: "What's the average tenant stay length?"

For example, here in Little Rock, Arkansas, the average is $245K.  

I am  grossing $93K/year  with an average Cash on Cash of 16.6%.