Could you give me an idea of what the average expected price I should charge for inspection services in the state of Nebraska? I know that HUD publishes a guide for preservation work, but is there a guide for inspection services?

It would be nice if you could set your own price but most companies now state a fee they are willing to pay and there is not too much room for negotiation. You need to have a solid understanding of your business expenses before agreeing to a fee because some companies offer fees so low that field inspectors net very little out of the gross fees.
The HUD guide does not specify particulars on inspections. The guide does say that $20.00 will be paid to the lender for the expense of the fee. When all the middle-men are through with that $20, you will see fees offer to you ranging from about $3.00 to $10.00.