I think I made another mistake. 

But people make the mistake of pulling equity with an old furnace and then that comes up in the dead of winter.

@Keenan B.Encourage you to learn from the mistakes of others - by reading posts here on BiggerPockets about owners not having their expectations met by their current Property Management Company.

If I made a mistake, besides learning from the mistake, I'll work extra hard to make the deal as best as possible. 

One common mistake is that investors look at the high market rent and assume they can get it, or they use an average rent but their unit is below average.

I think your mistake is concentrating on the North side.

Losing a little money or breaking even on a first investment is generally actually not a bad outcome if you can get a lot of on-the-ground learning experiences and mistakes out of the way early

Quote from @Bruce Cook: You should hire a professional property manager before you make a real mistake that costs you tens of thousands in losses.

Virtually no one in San Diego says 10 years after purchase that it was a mistake.  

I can't be sure, but it's an easy mistake to make at first glance.