If I can't afford to pay my property taxes, where can I get help?
There is no government agency that helps in this situation. There may be private charities or foundations; try "Googling" to find them (I am not personally aware of ones that do this, otherwise I'd make a recommendation.)
But first: even if you caught up on what you owe now, will you be able to pay in the future? If you can't--if the property is too expensive for you--then you best bet is likely to sell it now, use part of the proceeds (assuming it is not underwater on any mortgage, HELOC, or reverse mortgage) to pay the taxes, then find some place you can afford. I practice landlord-tenant law, and in a similar context, I find that if tenants can't afford their rent, then even if the somehow scrape together the money this time, they will fall behind again. They are much better off finding a less expensive place to live.