You are dealing with hypothetical issues so far.Its great you want to get "saving," but you know most people don't buy a house at 22. 

We prefer to make good quality updates to avoid continuous issues but obviously want to keep the costs minimal.

@Shafi Noss are saying a new lien can slip in between auction and issuing sheriff's deed? 

For instance, in a family-oriented neighborhood, additional storage might enhance appeal and facilitate a quicker sale, albeit with a relatively modest increase in value.It's essential to view these improvements from a value-added perspective.

The issue of adding a unit isn't all about construction costs, you need to investigate zoning and building requirements as well.

If for some reason you cannot, have the fee issued to one of you and have the one who received it to split it and then issue a 1099.

It appears as though there upper management and broker are better suited for vacation rentals and don’t Handel tenant issues well.

If the cash is more of an issue than the appearance you can always tackle the project down the road while on a vacation. 

They would each be putting in 200k each and I would be putting in 100k and would be responsible for all the property management, being paid by the other two on an hourly rate when responding to issues.

The cash flow from that property is close to nothing and if there are any issues with the property and you dont have the financial backing to handle it then it is going to be hard to deal with.