Since this report isn't for a lender, you could have an appraiser do a drive-by appraisal of a listing you might consider without actually needing access to the property.

My management software buildium lets them pay online. 

Follow up with your attorney or tax preparer to go over the details for your individual situation.I don't know of any checklist that exists for piercing the corporate veil but I'm sure if you read articles online, you would find several on the subject. 

I am researching and considering using an online service to help with rent collection, statements, and other administrative management tasks for my rental property business.

Make sure to attend the local REIA group if you want to get knowledge and access to some off-market deals.

Also if you are buying under an LLC did you have someone prepare it for you or did you set it up online yourself?

Besides the obvious that your place could get gutted and cleaned out of anything valuable, there are a number of scams where your listing gets posted to Craigslist, someone else gets access (IE via your lockbox) and "rents" your property to unsuspecting victims.If you do collect fees electronically, don't use Paypal.

I don’t have any other hesitation other than the total income they receive from their jobs not being sufficient (at least 2.5x the monthly rent), but should I consider the six months advance rental payments knowing they will have access to additional income made from the sell of their home?

They can allow you to access markets outside of your own, which can be invaluable.

There's no way I'd own more than a couple of houses without it, as the ability to leverage would be so limited that only the cream of the cream would have access to those funds.