Phil: I recently set up a 501.c.3 to help fund the maintenance of the Robeson Rolling Mill at the confluence of the Schuylkill River and the Wissahickon Creek, built c. 1700 per the Philadelphia Historic Commission and my research (build date could be later, worst case before 1777).
Long story about the Mill's history, but short part of interest to you may be relative ease of setting up the 501.c.3. I expect you can set up preservation agreement w/ township/county and avoid property taxes and nonprofits do not pay sales taxes.
I collected several sets of building preservation foundation Articles of Incorporation and happy to share ours and those too, and IRS application (1023 EZ). You can reply directly if interested (TreasurerWissMills@gmail.com) or call me @ 215 260 9900. Regards, Griffin Affel