Large banks like to limit people to 4 mortgages.

I have a limited amount of time to access the property.

For instance, the median price in Williamson County is around $75,000 less than within the (Austin) city limits.

My understanding is that there is a limit of 10 Fannie/Freddie loans per person.

I did have some trouble figuring out ARV due to limitations in the area with similar multi-family properties, so honestly I have no idea if thats even close.

Compared to an IRA, Solo 401k contribution limits are roughly ten times higher.The Solo 401k will allow you to take participant loans while the IRA does notThere is no custodial requirement for the 401k.You don't need the additional expense and administration of an LLC to have checkbook control.There is a built in-Roth component whereas IRAs are either traditional or Roth, not both.A spouse can also participate in the same Solo 401k plan.

We reviewed the international Property Maintenance Code (https://codes.iccsafe.org/content/IPMC2018/chapter-4-light-ventilation-and-occupancy-limitations).

If he provides all the capital then he is a Limited partner.  

It is a full time job in itself and will tax beginners to the limit.

Maybe the seller's agent would be willing to give you limited access to look at comps?