Drive Surgeon,
You need to consider what you think a job/contract is going to cost you before you even consider making a profit.
You need to consider some of the following (In no particular order);-
1, wear & tear on your machinery & vehicle, and costs for replacing parts/labour.
2, chemicals & sundries needed to carry out the contract.
3, your hourly rate for doing paperwork and call-out situations.
4, costs in seeking legal advice & drawing up legally binding contracts.
5, travelling costs, road tax/mot your vehicle and insurance.
6, costs in seeking hired help.
7, costs in purchasing licenses for water usage.
8, costs in hiring replacement machinery if your washer breaks down.
9, costs involving stationary.
10, public liability insurance.
11, Accounting costs - setting up a limited company perhaps?
12, advertising costs
13, How long is the job going to take to complete?........and to allow for unexpected situations that are out of your control.
14, you need to consider how late payments affect you
15, VAT & inland revenue
16, will you have to hire machinery for specialist tasks?
17, what is a job agency going to cost me if i can`t find staff?
If you are going after government contracts, they sometimes insist your bank can promise you a loan (bond, normally £25k),....before you will ever be considered for a contract bid, .......this to satisfy them that you have enough money to carryout the contract (pay wages, buy equipment, buy sundries etc).
You are also going to have to show your previous 3 years accounts as proof that you are a capable/sound trading business.