@Caryn FischerI agree with Jaron, you should definitely have a consultation with your tax accountant and/or financial planner before you do anything. 

If they're doing anything another tenant would complain about I send them a written warning and the minute another tenant complains is when I'll double check to see if I can file eviction for that specific thing and give the tenant three days to knock it off. 

You could just let the money build up in your checking account.

I also really like looking at a giant balance in a bank or brokerage account.

It doesn't even take into account the pref!

I have some of the required funds in a HYSA, but will most likely need to draw from another account and I'm curious which method is the most efficient in terms of taxes/capital gains, penalties, loan repayments, etc.Based on my previous transactions in the market, I estimate ~$45k cash to close: $20k for the down payment, $15k for closing costs and prepaids, and $10k of starting reserves.

Make sure to account for property taxes, insurance, and any HOA fees, as those can vary significantly in different markets and impact your cash flow.

So if they can get guaranteed 5% interest in an account they can get their money out of at any time they’ll want 8-10-12%. 

The only item I would suggest is double check the payment terms of the your HELOC... in particular, can you pay interest only or are you required to pay a portion of principle each month on the amount utilized.

Account holders can't take any write-offs personally for investments made in the 401k.