No the tax would be paid in closing on the house purchase price, and the closing fees, and any other service charges. And it would be included in the amount that you get the loan for, and then you would pay FairTax on every loan payment for some percentage of the interest.
And you would pay the full amount of FairTax. In this case, if the house was reduced from $300k to $276k by the elimination of 8%, then the FairTax paid would be $82,441 if the FairTax was 29.87%. (Of course, the FairTax rate would be really much higher, probably closer to 50% but I'll leave that for now).
This $82,441 would be paid at closing and added to the loan amount. You would add this $82,441 together with all the other taxable purchases (including the FairTax in part of the interest on your loan) you make over whatever time period you want (YEARS DON'T MEAN ANYTHING UNDER THE FairTax) and subtract the prebate entitlement welfare payment to CALCULATE your actual rate.
You would have to spend nothing else (besides the interest) for probably ten plus years in order to get your FairTax "effective" rate down to 15%. And it is likley that as the FairTax system started to break down, the entitlement prebates would be eliminated completely for anyone who could still afford a $300,000 house.