at this stage I would encourage him to put the cash in a brokerage account paying 5%  like T bills and keep searching and as well I would also advise to househack first before buying low end looks great on paper rentals find a nice duplex buy it live in one side rent the other rinse repeat.

I only got involved after I did all of my homework and actually knew the people behind the deal.

Maxing out retirement accounts, ira, adding to taxable accounts (index funds) for pre-age 59.5 access.

. , who got me involved). 

I'm a landlord and I will have a new tenant since my old tenant don’t want to renew the lease, So with this new tenant I want to use the auto-pay debit from tenant's bank account and send it to my account, in order to avoid late payments and stress.

While it’s true you have to have a custodian for any ira the fees vary and if you utilize the checkbook control offer - essentially a special purpose trust or LLC is created and all the investments go into and out of that account owned by the trust or LLC.  

Honestly in my market with interest rates, rent and house prices-I'd put it in a high yield savings account.

On the city inspector I'll try but likely no consequence, our attorney says municipalities are not held accountable for things like this 

Even worse some local municipalities are involved in the process to the point those cities are not investing in.

Account for increased A/C costs and manage the rental agreement to avoid parties.