I will be on cancer treatment for the rest of my life. husband has heart failure.

I think an interesting alternative to sharing one's profit margins may be to show other flippers how much you can save by going the DIY route as opposed to subbing everything out.

In the past tenants have used window ACs but have resulted in significant water damage in the walls.Question: I was considering alternatives to window ACs including: central AC, split mini ductless AC, through the wall ACs, or portable ACs (ones that look like dehumidifiers).

Alternatively, or in conjunction, you could have them pre-pay first and last month's rent and deposit, and escrow the rest, such that you are always at least one month ahead of them should eviction become necessary. 

If there is an alternate residing address listed for the owner, I send a letter to them asking if they are interested in selling their house.If there is no alternate residing address listed, how do you suggest I go about finding and contacting the owner of these abandoned houses?

The tax treatment for your rental properties is the same whether you own the properties in your own name or in your LLC.  

Alternatively, you could sign the tenant on a short term lease, say 3 months, to vet them out but charge a premium since they don't have much of a reliable back round. 

What are the alternatives?

Get some of that "frosted" look window treatment from the local home improvement place - not a heavy pattern, but enough to to allow the light to still come in, but blur or remove the view of that gas station.  

@Rose Martin - when you say "shutters" are you referring to exterior shutters or interior window treatment?