Hair should be grown at least 4 weeks before a wax.
Hair grows in 3 stages, so you want to make sure all 3 are long enough to wax,by 4 weeks it will be ready for a wax. Make sure to NOT shave in-between waxes!!
Make sure to exfoliate before you come in and starting 2 days after your wax(then every time you shower)to help remove dead skin and keep ingrown hairs away.