When you arrive you will have to buy a tourist card for $10/US at the airport, which is valid for 30 days. You'll see them being sold at a desk before you get on the immigration line.
You may have to pay an additional amount [small] when you leave because you stayed over 30 days.
AE
The small amount will be 800 pesos.
B - IMPUESTOS POR ESTADIA PARA RESIDENCIA PROVISIONAL O
TARJETA DE TURISTA
VENTANILLA EXTRANJERIA
CODIGO DESCRIPCION TARIFA VIGENTE VIP
032 De 30 dias a 3 meses 800.00 -
033 De 3 meses a 9 meses 1,000.00 -
034 De 9 meses a 1 a?o 2,500.00 -
035 De 1 a?o a 1 a?o y 6 meses 4,000.00 -
036 De 1 a?o y medio a 2 a?os 5,000.00 -
037 De 2 a?os a 2 a?os y 6 meses 6,500.00 -
038 De 2 a?os y medio a 3 a?os 9,000.00 -
039 De 2 a?os a 5 a?os 14,000.00 -
040 De 5 a?os en adelante 17,000.00 -