Two rules apply:1) The cost of the replacement property must equal or exceed the price of the sold property (less actual selling/closing costs).2) Seller must reinvest All of the cash received from the sale of the property, to totally avoid taxes.  

Keep in mind if you are going to purchase the property in an LLC there will be different rules.

I use that 100x rule as a way to analyze a property super fast.   

In my market, I like the ARV to match the 1% rule, and typically think borrowing up to about that is a good mix of being conservative, and getting some cash flow. 

Property taxes are specific to states and cities, There is no universal rule on them covering the entire USA.

.: It seems like a good option however I don't have experience in buying properties out of state ( I am ruling this out for now).

Also if you got owner occupant specific financing you may need to refinance it anyway to stay within the lender's rules.

But there is a 20% down rule based on purchase price plus rehab dollars needed.

He has not made much effort to abide by HOA rules or listen to us when making decisions that affect both parties. 

Rules for renting out your basement vary greatly by jurisdiction here.