you really need to see a tax professional to go over your tax situation. This may include revoking the S-Corp election.
the problem is that the S-Corp does not own the property and yet is using it for its business. this is not arms length so the IRS could attack this. when you were an unincorporated business you were taking or should have been taking depreciation on the building. you don't need a lawyer to draw up the lease, some websites for a fee will allow you to use a proforma'd lease to which you make whatever modifications you want.
another important factor is that should you ever sell the building, the tax laws require you to recapture the depreciation you took or in your situation more importantly the depreciation you should be taking on schedule E. that's where the real estate taxes get reported if you paid them.
the lease could require the S-Corp to pay the real estate taxes as part of the rent. this would reduce the fair rental the S-corp otherwise should be paying you. but again I don't know your entire situation or your knowledge of the tax laws affecting interactions between you and the S-Corp.
I'll bring up another point since you and the S-Corp are two separate tax reporting entities. have you taken a salary from the S-Corp? if not that would be another red flag for the IRS when you file the S-Corp return. the return for a calendar year S-Corp is due 3/15 of the following year not 4/15 as some suppose.
one of the main reasons for an S-Corp election is to avoid self-employment taxes on all the income that a business makes. 1/2 the medicare and social security taxes come out of your paycheck (a reasonable salary is required) and the S-Corp pays the other half. The rest of the S-Corp profits are not subject to these taxes whereas as an unincorporated business you pay those taxes on all your net business income but do get a tax deduction for 1/2 of these taxes.
there are other advantages and disadvantages to the election best discussed with a tax advisor. one might be having to file a separate tax return for the S-corp which if on a calendar year needs to be filed by 3/15 of the following year. not 4/15 as some suppose. late filing can result in penalties of $200/month.
