Ask in the remodeling forum, and include a measured floor plan showing the whole bottom floor.

And does this have a basement access? Or maybe is next to a basement?

There is a shed underneath? or an underground garage that is not used as a garage
Thank you

You need a 3" drain pipe and vent for the commode, so it depends on where your other plumbing is located. If its all on the other side of the house it may take a lot to get a 3" drain installed for the toilet.

We have a dutch colonial with a screened side porch on a poured cement floor that is one step down from the adjacent living room, and we are considering adding a bathroom for the 1st floor (there is only an upstairs bath and a basement bath). During a basement renovation we had them trench in additional sewer drain pipe that ends with a vertical stack in the basement right next to the porch.

Since you want to keep your space for the office, you also have to decide how big you want make that 1/2 bath. We want to allow for handicapped/ADA access, so we need quite a bit of space for the 1/2 bath and will have very little left for an office area.

Bruce