I prefer not to do roofs anymore but its not out of the question.I have been putting together a team lately consisting of an agent who works with sales and rentals, a broker and an accountant who invests in property himself and has been a personal friend for years. 

This would be a fully rehabbed property, so I am expecting CapEx would be low, but I want to make sure I save up enough during say the initial 5 years so I don't lose money when say a roof needs to be replaced.  

a roof is a roof regardless if rent is $450 a month or $800 a month. 

A chunk of the kitchen ceiling has fallen down but the roof appears to be in good condition.  

Issue are: roof, windows and bricks.Thanks

For example, a roof has an average life of 20 years so each year you should put 1/20th of the cost of a new roof in reserves.

That could mean anything from unsafe steps, non functioning or inadequate heating, leaking roof, to a biological hazard such as human or animal waste. 

I would think about the cost of a roof, various plumbing expenses, electric work along with 6 months of PITI.

The roof will need about $18,000 of repairs (rough estimate) in the near future because of deferred maintenance by the current owner.

Let's say the water heater started leaking and ruins some clothes, or the roof leaks, or their refrigerator goes bad and ruins their food?