I am responsible for water, heat (gas or oil), common area electricity. 

You touched on alot of points and have some common ideas that most people have when they are starting off. 

@Ignacio Linares Its not impossible but its not common.

One person might be taxed at 30% while another might be 47% in a higher bracket and higher tax state.The most common way to reduce tax liability from flipping houses is to refinance them and keep the flips as rentals.

It's extremely common for buyers in the Austin market to waive the appraisal contingency to win in multiple offers, which means they are removing their right to terminate or negotiate if the appraisal doesn't meet value. 

You don't want to put yourself in a position where the balloon comes due and the capital markets have dried up (i.e; 2009-2011) With most commercial loans, there are 4 items that are commonly negotiated or massaged: the % loan to cost, the interest rate, the amortization rate, and the length of the balloon payment.

It's a common mistake to start rewarding yourself too early.I started investing in 2016.

That type of contract is pretty common, although we don't always require it.

You'll likely have to cover common area electricity and all of the water (typical for Chicago may be not your case).  2. 

You should know rents, common expenses, vacancy/occupancy rates, etc.