It used to be that the rule of thumb was $1000/month carrying cost (including taxes & maintenance) for each $100,000 borrowed. Exotic loans and teaser rates changed that.
PC I think you’re confusing the 1% rule. When the monthly rent collected get’s to 1% of the purchase price of the home(SFR), you can expect to get cash flow positive. Anything less and you are cashflow negative draining money from yourself.
For condos, high mello-roos and HOA areas that is slightly higher due to the extra fees. (Some argue that it cancels in slightly less maintenance).