There have been a lot of great responses here already and I'll try to be brief in my response. Seeing that I wrote most of the data recovery related resources, you can refer to them to get my advice on how to handle cases.
A) It seems to me that by offering data recovery, you may get new clients through the door who need your other services, such as replacement drives, backups and regular maintenance. They should be an easier sell, as they already know how bad a hard drive failure can be.
B) Start by outsourcing to a trusted partner lab who will work with you. As you gain knowledge and skills with certain data recovery tasks, you can consider investing in the necessary hardware and software and slowly take on more in-house.
C) Depending on who you partner with, their pricing will have a huge impact on how your client decides whether or not they want you to try vs sending it out right away.
Examples, based on base rates of a typical hard drive (retail prices...discounts/commissions may apply)
Data-Medics - $275 USD
Recovery Force - $400 CAD (~ $300 USD)
300DDR - $300 USD
Seagate - $699 USD
DriveSavers - $700 USD
Take note, anything you can do yourself should likely be done at the lab partner's minimum rate...though some labs rarely charge their minimum with a sales team trained to charge as much as they can.
Another thing to note. I have received a lot of crashed hard drives that I have to call unrecoverable after the technician tried all he could think of first. The technician tells their client that data recovery costs thousands by professional labs and then tells the client that they really have nothing to lose to try it first for much less...and then say, if we can't get it, we can still send it off to a lab for a quote.
Don't be the tech who takes a recoverable drive and turn it into this: