Hard drive repair solutions

[teradost]

I am starting out my computer service business in the part time, and have had some calls come my way. I have been able to solve them all, except for the ones which relate to hard drive failures.

So, now I am looking to invest some money into some hardware-software that I can use to recover data from these hard drives for my clients. I can recover data from PATA drives by setting them as slaves in my system, but I cannot do anything about other types of drives.

So now I am looking at different enclosures and adapters which allow you to connect SATA drives to USB 2.0 and such, and have only been able to find enclosures for 3.5" drives.

My questions:
(1) are 2.5" SATA drives popular, or are they something you encounter once in a blue moon
(2) is there an adapter or enclosure which will allow me to switch back and forth from 3.5" and 2.5" SATA drives, or does one HAVE to buy two different enclosures
(3) what is the best way to go about setting up SCSI drives for repair --- with PCI adapters or enclosures or something else
(4) what different SCSI types are out there, and is there some type of hardware which supports them all

any help would be greatly appreciated

thanks