I'd expect more turnover and more maintenance costs than you may have budgeted for initially.Below is a link to the comps that I thought most resembled the subject property. 

@Samer JaberThe arrangement that I made with my brother was that he would get a slightly discounted rent. 

Formal breeds often considered to be of the pit bull type include the American Pit Bull Terrier, American Staffordshire Terrier, American Bully, and Staffordshire Bull Terrier.[1][2] The American Bulldog is also sometimes included.[3] Mixed-breed dogs which physically resemble these breeds often get labelled as "pit bulls" by shelters.

This type of arrangement has the maximum benefit for the agent and the minimum benefit for buyer and seller. 

But for the past 3 winters I’ve had an arrangement with a neighboring business that allowed my tenants to park there overnight.

We will write a proper agreement spelling out all expectations and obligations, and use an attorney to make the arrangement proper and official including a buy-sell agreement, etc.We can likely buy and rehab our first property with our combined cash and without need for an initial loan, although we may want to get a loan after the rehab to get the cash back out, BRRRR style, and/or for subsequent properties.

He should receive the security deposits at closing unless you have other arrangements with him.

This kind of arrangement is pretty innovative, so there's no guarantee that you will find something similar in your area, but you never know.

We have a couple options as I see it (using an assumption that the market value is say $800k for the purposes of this discussion): Dad takes out a loan to "purchase" the house from the estate and arranges to give my aunt $400k.

We take this opportunity to talk about parking and public transportation options related to the property they are viewing.We ask the applicant to call us when they are finished with the application.We arrange to pick up the application in person at the applicant's current residence, if we can.