If the second home is used entirely for business, the expenses for the home can be fully deducted on schedule C as a business expense. You only need to use form 8829 if a portion of the home where you live is being used as a business space.
I have the same situation. I have a second home, not used for personal use, entirely for business. Where/how would I deduct this on SCH C?
Q. I have a second home, used entirely for business. Where/how would I deduct this on SCH C?
A. You deduct the expenses individually, e,g. mortgage interest on line 16a of Sch C, utilities of line 25, and property tax on line 23. TurboTax (TT) will present entry screen(s) for each of these expenses. There will be a separate entry for Depreciation of the building asset, which will go on line 13.
How are you using a "second home" "entirely for business"? If the home is being rented out, then it is entered differently.