Outsourcing your support always sounds good, but it’s really a bad idea in all but some extremely specific scenarios.
First, support is a PROFIT CENTER. It’s really key, especially for bootstrappers who have little to no money for customer acquisition to nail every customer interaction, capture every bit of feedback, read between the lines on every half written reply, etc. Someone from ODesk is unlikely to give that level of consideration to each email.
Also, unless your app is extremely simple, you’ll need to pay a pretty substantial amount of money to train the person and as this is just a temp that’s a lot of money and worse, your time, being wasted on someone who might disappear tomorrow.
Nearly everyone is better off finding someone who works on a part time or contract basis with the understanding that this is a job and you’re part of the team vs setup as random hourly work which may go away for them at any moment.