In the end this kept their payment the same, I pocketed more on a monthly basis (difference that manager had been stealing) and I have had someone make timely payments for 5 years with no repair expenses on my part.

Many reason I stay away from Condo's including:HOA regime feesUnexpected and expensive HOA assessment fees for upgrades or repairs that you may not agree with.RulesClose proximity to others that could cause disagreementsSaturation and competition on renting condo's ParkingI would personally never buy a condo for these reasons and look for a deal on a house.

That’s part of why I was reserving 10% of the rent for repairs and another 10% for CapX.

. - Understand the upside of the "rent by the room" strategy- Understand the upside of any repairs that can be made to the main unit. - Understand the cost/value of completing an ADU project- Underwrite mid-term and short-term upside cases as well. 

However, he didn't include repairs, property management, CapEx, PMI, misc., etc., so the $3-400 'cashflow' would probably be closer to $0 or a loss on the property they were analyzing. 

Monthly cashflow does not account for vacancy, repair, cap ex.

Vacancy, capital expenses, and repairs would be the big 3.

I'm preparing to repair/replace HVAC and plumbing.

If you do that, you must put a cap on taxes, insurance, and repairs......and that will never happen. 

As you may know, a good portion of your monthly rent will not go in your pocket, it will go to the constant maintenance, upkeep, repairs, taxes and the like.Fourth, ask yourself... if you have a vacancy, the economy goes in the tank, you have huge unexpected repairs, etc....will your tenants chip in to help you out?