Retiring from a portfolio of rentals

[Robert L.]

With a buy and hold strategy accumulating SFR rentals into a portfolio for retirement, let's say you cash flow an average of $300/mo per house (after all expenses/mortgage).

If I was to generate like $9k/mo in order to "retire", that means I need 30 houses, correct?

Don't want to sound negative, but I've talked to investors with a large portfolio of houses and they complained to me that profits were eaten up by costs such as replacing roofs, replacing AC's, vandalism or other issues from tenants, evictions, etc.  They even advised me "not" to do this.  Well, I've also heard from others in this forum that this is "the way to go".

My question is for those who have a portfolio of houses if you are truly able to retire even with the high ticket maintenance costs such as roofs, AC's, etc.? How do things look for you?  

(side note: I've even considered venturing into multi-family units instead so 30 houses won't seem so daunting)