Changing out interior doors in house. All of them. Going from brown crap to white 6 panel. I have two hinges on each door. Would like to buy new door with predrilled knob hole, cut it down correctly to size, and then attach hinges to it. Only issue I have so far is not really sure how I should cut out for the hinges. I have read use a chisel. I am fine with that but do see how I can be even going across.
Do you have access to a router? You'll save yourself a huge amount of time if you buy a hinge mortise template (like this one from HD) and use the router to cut out the mortises:
They attach temporarily onto the edge of the door, and you use the router in the large opening to cut to the correct depth. Once you're done, take the template off the door and screw in the hinge plates. Done!
I would recommend against buying pre-drilled as it probably won't match up with the existing jamb holes.
I recently replaced two doors, and at ~$10 found this to be the economical solution:
It comes with two hole saws, a latch template, strike template, hinge template and a router bit for your drill or router if you have one.
The hinge and strike plate templates work with the router bit to create the edges of the mortices. Then chiseling out the interior is dead easy.
When I mounted my doors, I removed the old ones and transfered all measurements to to the new ones. I cut the bottom to size with a table saw, and dry fit the blank before doing anything else.