My basic advice is, don't over complicate it by having a vendor in the middle of it until it is worth managing the vendor. If you are dealing with adding 3-4 employees every few months it isn't a big deal, even a couple a month isn't a big deal. If you are doing 7-10+ a month then it is worth paying someone to manage this. Other factors that can affect the decision, if you have no physical office to store equipment, you may need a service provider to handle return of equipment when an employee leaves etc.