The 1% rule is best only used as a quick and dirty evaluation used to pick which property you plan on running additonal calculations on.

For short-term rentals (STRs), the 100-hour rule may be an easier path.

Do you guys still apply that rule? 

@Anthony Sigala that "Rule" was created for mostly Class B properties BEFORE the Great RE Crash of 2008-2010.Values after the Crash dropped so much, that it could also be used for Class A rentals.Values are now more than their pre-crash highs, so the rule now only applies to Class B & C rentals.How are you identifying Class B & C submarkets in your area, so you can properly apply the rule to the right rentals?

@Seidy Lasker Wash sale rules apply to stock options if they are deemed "substantially identical" to a security sold at a loss within 30 days, such as options with similar expiration dates or strike prices.

Typically 75% of rental income can be applied towards your DTI for qualification. 

Yes, a rule of thumb COULD eliminate a good deal if not applied correctly.

The 50% rule - in my opinion- is used solely as a quick back of napkin calculation to determine if it is worthwhile to do more investigating of a property. 

Or maybe a favorite way to stay updated on local rules?

Prospective tenant views apartment and decides if they want to apply.3.