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?

Don't limit yourself to believe that it can't be done while you are living in Germany.

The banks diversify as many way's as they can to limit the risks and maximize their returns within the regulatory limits.2.

It's not just about net energy cost savings, although that's the easiest to measure.  

@Dayne WintersHoboken (preferably Downtown),Jersey City (Anywhere off the "PATH" Train, note the Waterfront, Downtown, and Newport are nicer than Journal Square)Manhattan (anywhere really but the nicest areas are anywhere south of about 70th street)Queens (Long island city, or Astoria near a subway stop)Brooklyn (Downtown, Heights, Carroll Gardens, Park slope, Williamsburg, there are others but that's just the short list)Since your question is a bit limited I am unsure if this is business or vacation and if it is with children or without.