If you're looking for software with strong rental accounting capabilities though, there are apps that have this functionality built into them (rather than paying extra through RentRedi to use the REI Hub.

If you still like the deal with those conservative numbers, then any extra function from the converted room is just a bonus for tenants or end buyers.

What is in it for you is not just the bump in monthly rent but also a boost in overall property value, since a larger, more functional lower unit makes the home more versatile to buyers down the road.

Decks usually aren’t my favorite because of their maintenance costs, but in this case it created great outdoor living space that made the home much more enjoyable and functional.

Exploring other options like Appfolio or Apartments.com which might offer the balance of support and functionality you need, is a sensible approach.

Quote from @Geeta Bihari: Cash flow will be a function of how much money you put down/amount of leverage you use. 

What are the functional issues? 

Prices are always a function of low supply and high demand.

Make sure any lender requirements—cash management, carve-outs, reserve controls—still let you function as co-owners.

Are there any other people currently prioritizing design over income/functionality (that isn't already a multimillionaire)?