If you're buying the house using traditional fannie/freddie loans for investment properties vs if you're using non-qm financing (say a DSCR loan), the answers will vary. 

Say a $500 range would allow u to deduct $100/yr for 5 years whereas a $125 repair to your existing appliance would be fully deductible year one.

I'd say a 3/2 under a mile from beach in right area can do $5-$7k per month in vacation rental gross rev.  

So most lenders looking at say a $4,400 rent duplex with an $1,840 PITI would not be adding the debt to my DTI but adding $1,460 to my income. 4400*.75-1840=1460I have had rental property for 4 years but only started really pushing to get more in the last year.

If they don't get insurance and say a leak damages something of theirs I can point to the lease.

This lets you get started investing especially without personal income requirements if your personal income is not there yet to qualify for say a conventional loan on an investment property. 

@Parker FairfieldThat's difficult to say as there is not one thing/metric I look at.

For a builder I would say a flat roof is much easier and more economical to build. 

This is a big pig or should I say... a "porker"? 

What would you say a reasonable number is to reach off of an avg engineering salary?