They say they’ll wire me 12k in the beginning and then I have to pay $3k rent each month
Make sure your rental contract specifically states the rent is $3K a month and nothing less. Also read the contract for what your liabilities are for early termination. Generally, a rental contract is where you agree to pay rent for an entire year (or whatever the time period is) with payments due in installments (usually monthly). So legally speaking you are obligated to pay a total of $36,000 for a year's rent - but payable in monthly installments of $3,000 a month. So if you move out after say, 2 months, you are still obligated legally to pay the full $36,000.
If you are military subject to change of station due to PCS orders, ensure there's a military clause in the contract, and that what happens with your rebate is clearly spelled out.
