The buyer will pay the RE taxes on the property typically. I guess you could get a concessions for them in the first year or worked out with the buyer in the price or cash back at closing; though because its seller financed I doubt they would do that. Because you will want it recorded that the transaction has occurred there really isn't any way around this. I guess you could get something like a quit claim deed, but that would be bad on the sellers part because he won't have much for insurance that payment would actually happen - and I don't think you could do that at a title company because they have ethics regulations about that (everyone would just quit claim deed their house over for $10, and you would by a paper clip for $200,000 and then there would be no basis for taxation)
Besides the money won't really be made in the 6 months to a year by; the time you recoup your buying expenses, any repairs or upgrades you need to do the property or just rebuilding reserves. But more over, if the property taxes are going up are going to kill your deal, how are you going to deal with inflation of services such as water, sewer, trash or general handyman/materials for the project? Our water/sewer bills are all expected to rise about 8%-11% this year.