You cannot use a HELOC as liquid reserves since it's a open end liability.You would be better off taking cash out of a property and securing it into an account checking/savings and allowing it to be "seasoned" for 3-4 months prior to putting in the application. 

Something I have noticed is we tend to occasionally have a tenant who seems to think that rent is due on the first for the prior month.Despite late fees, constant reminders, etc. they will without fail pay their rent one month late.Aside from threats to evict, is there a better way to screen tenants like this out ahead of time?

Always call to verify the wire instructions you have prior to making the wire. 

Owner has listed this property 3 times prior and lives out of state.

So far I wasn't given any check in/inspection list from the previous owner and wandering what everyone has done in these situations where it looks like the current tenants seem to  have done some damage more than just your wear and tear but you don't have a list to see what status it was in prior.

In Austin, its better than what it was a few months prior but its a little high.

My last bill was $100 less than my prior years bill.  

The rich generally get that way by using the levers available to them- hard/intelligent work, smart advisors, the decline in interest rates for half a generation inflating assets beyond all prior expectations, or, in DJT's case, having a rich daddy(what a lovely zygote.

I would definitely recommend you build up your cash reserves prior to jumping in.

At the beginning of your addendum, reference the prior "rental agreement" or whatever it is titled, the date it was executed, and all of the named parties.Then clarify the changes you all agree to, which could include just the parties, or also change in length of term, or, change in rent amount, and all sign.The addendum should address how the SD is handled, but may vary depending on terms of existing agreement.