Second to cash in the bank is HELOC cash because you can use it however you want (you just have to see it already in an account).

MLS usually get's you the highest price but you need to account for the higher closing costs.

Maybe look at numbers and properties you could do a potential house hack and begin to plot out moves but I don't want you to fall into the analysis paralysis group and never make a move, have people that will encourage and keep you accountable. 

Like I said, I'm not an accountant so you should probably talk to one.

Maximizing cashflow becomes a strategy choice that accounts for your market and tenants.

Each multifamily building I have has its own bank account.

How much is reasonable for management, accounting, and rental commission fees?

Mostly people with minimal RE experience are adding a single ADU and they often make that choice based on cash flow without taking into account the negative equity position.  

•Set up your EIN and operating agreement.2.Set Up Your Business Bank Accounts:•Open 3–5 business bank accounts to give your money purpose:•Income Account: For revenue and deposits.

Account Closed I have no information regarding the Due on Sale Clause.