The best part about it is it's easy to tag your transactions for each property with categories that sync to your Schedule E for taxes, making tax prep super easy.

I think some markets, mainly the STR runners, have another 10-15% to go then the markets hit by HOA/HOI/Taxes still have a bit more correction to go for. 

You likely won't be able to take any deductions on your personal income, but real estate does have tax benefits.

My understanding is that whatever "net income" I have from my rental is taxed at whatever income tax bracket my wife and I are in.My wife and I file jointly and our taxable income puts us in the 25% bracket, so my understanding is that if we make say $4000 net income from our duplex then we pay $1000 in fed taxes on that.Are you saying that is incorrect?

I do work a full time job which is my primary income as well. 

Figure a few grand to paint rooms, replace carpet in a room, deep clean and spruce the property, replace a fixture or two, etc.If you have to replace your resident annually the $9600 total income will get a gut punch.The true value of the higher-end neighborhoods is residents know if they move out of the home they have it's a challenge to find another, especially if they have been there a few years and have a competitively rewarding rent rate.All this really is is basic economics...sell ten custom widgets for $1000 or 100 standard widgets for $100 each.

The AirDNA estimator calculates a $16,000 annual net operating income.

Can they be used to cover or prepay the property taxes?

If you finance at 25% down, 25 year amortization and a 7% rate you will not cover mortgage and interest let alone insurance, taxes, vacancy, repair, etc.

After five years you'll have earned $90,000 in rent income and gained $34,000 in appreciation.Buy four houses with $50,000 down on each.