The biggest thing there is TRAINING. What is your sales guy selling? You do need some way to differentiate yourself from the competition.
If you already gotten into all the usual networking things (BOMA, etc.), and have made your 'marketing' money there giving you the returns to justify doing some 'growing up', then I'd say go for it.
Also, make sure to tie their compensation to performance. This is an obvious one, but so important. Track their appointments, make sure that the expenses you pay for get you value. Make the salary a barely-make-it-by proposition, and be creative on performance based pay.
CREATIVE here is key. Things like paying for health benefits if they meet goals can be priceless (and doesn't have to be expensive). Maybe offer them residuals, tie them to all that business they found you - also making them a good ongoing resource, they'll care that your customers keep feeling happy.
The biggest thing of course is having a selling proposition that gives you short sales cycles. I can offer some suggestions here, depending on how specifically you run your operation (all are different ... construction clean-up vs. office cleaning, specialty services, etc.)
Drop me a line if you need more pointers.