Also, there were too many interior walls to make mini-splits the economical choice - we would have needed 3-4 interior heads. 

During this process the tenant has asked that interior pictures are not used because it would show their "stuff".

., this is usually dictated by lot size and land development code limitations, not what will sell.In the past I've done a lot of clean, white and grey contemporary interiors.

The home is in good condition from the upgrades he made and he's painting the interior next week before allowing it to be viewed.  

If the Architect wants $7500 to draw up plans and attend 2 meetings/walk thrus through the project, and an interior designer wants $5000 to do their design, finish choices etc...

I recommend an interior and exterior paint within the next year."

The replacement windows are installed from the interior, they but to the exterior trim/brickmold and then attach.

Do the interior renovations as they become vacant like you mentioned. 

I say it's apparently nice because he didn't want to let us see the inside, but the outside is in great shape and one of the tenants told us he's been inside and it's "gorgeous and huge" with no interior walls. 

Knowing whether you can get that depends on your exact location, the aesthetics of your interior, whether there's parking, and the other amenities in your building.