Should I be buying leads?
If you are having trouble keeping your prospect funnel full, then yes. How do you know if your prospect funnel is full? Focus on appointments and not sales.
Example: If you are looking to have 12 new sales per month, and you have a 15% closing ratio at appointments, you need to have 80 appointments per month.
Do not forget that leads should be supplementing your current marketing efforts. The leads you are buying should not be your only source of new prospects.
Which leads should I buy?
What kind of leads do you want to work? If you have no desire to sell over the phone, then do not buy telemarketed leads unless they are pre-set appointments. This also works the opposite; if you are looking to only sell over the phone, then do not buy leads that would have an expectation of a physical appointment.
If you are investing in leads, then make sure you are going to put your maximum efforts to maximize your return on investment (ROI).
NOTE: It is important to track your cost-per-acquisition (CPA) to make sure the lead method(s) you are using are producing a profitable source of sales.