If you contact the county building department, you can get a copy of the house plans. These will have the original design firm on the drawings, I have a set for my house. These will also have an indication of any interior walls that are LOAD BEARING, ours has 2. There is a wealth of other information on these. I would get these first, then you could try contacting the original designer, or your own for opinions on whether what you want to do can be done. Some of the large firms (T&D comes to mind) may be willing to meet with you, however, the last time I dealt with them it was a 4 to 6 week wait for the initial meeting!
If you are not familiar with TV homes, most if not all of the plumbing is in the floor, none in the attic, and only risers in the walls.
Also, if you know the model of the house, you can ask on here if other people have done similar modifications.
Now one final word of caution, for ANY and ALL home expansion projects you will need to contact ARC,
VCDD Architectural Review or phone 984 Old Mill Run, The Villages, FL 32162, Community Standards Phone: 352-751-3912. This step is very important, because without ARC approval your project is dead in the water.
Hope this helps, will be glad to talk on the phone in greater detail, send me a PM with your phone number.
Hope this helps.
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Pennsylvania, for 60+ years, most recently, Allentown, now TV.