Calculating rehab expenses

I was wondering what would be the best way to calculate my rehab costs? Should I just get quotes from a sub-contractor? Or should I call each company (ie carpet, paint, roofing) and get quotes directly from them? Also it would be very helpful if anybody could add problems or personal experiences that they’ve had in this area to hopefully avoid any unexpected bumps in the road. Do those in the rehab business find your estimates to be pretty acurrate? This is the only area I lack confidence in and any help is greatly appreciated.
Thankyou in advance.

You should receive at least 4 bids:
I Suggest…
1 from home improvement store like home depot or lowes (this will give you a good idea on materials and labor.
1 from referal from friend, other investor, ect.
2 from General contractors in the yellow pages.

Do you find that the bids are within relative range of one another? How much should I expect a bid to cost me?

The bid should not cost you anything. The costs can vary by a large margin. You will have to find the best price AND quality…that is why you should receive multiple bids.