I own a home and my son lives in that home. I live with my new husband in his home.?

When my son has better credit I will sell him my home at whatever is left on the mortgage. Now this Homestead exemption has come up this year and I'm not allowed to take the exemption since my primary residence is at my husband's home. My name isn't on his mortgage and his name is not on my mortgage and we file married but filing separately because of the two homes. My son and I pay the mortgage together, but he doesn't claim any rent on his taxes and that is why I will sell him the home at the mortgage balance when he is able to buy it. Since I own my own home and my husband owns his own home and we file married but filing separately, is there any way I can file the homestead exemption and my husband can file it too? The property taxes on my home have it valued at $105,000.00. My property taxes are about $790.00 right now. What can I expect if I can't file the homestead exemption?