Whithunter, the answer to your queston is yes, you need a contract, the answer to the other half of your question is also yes you need to go to an attorney or several attorneys to get help in writing one up, I"ll explain why, every state and area is different and the legal aspects are as well, you need to spend a little money ahead of time to avoid problems later on, think of it as preventative maintenance and how to avoid collection problems later on and just go seek legal help. They will help draw up a work atuthorization form along with estimate forms and bidding forms and a change of work form and so fourth. You need to be protected and have signatures in place so if things go bad you have more than the usuall he said she said bull to cover your butt.
I've been where your at and got tired of it as well, you spend more time and effort to get paid than the work you did in the first place, not to mention all the headaches to go with it. Here's what I did and why and how its worked for me.
I had several attorneys draw up a work authorization form and took it to several more and had changes made until I came up with one thats simple and easy to fill out, takes a few minutes to do and has a place for two signatures, mine and the customers along with a date for each to put in. a place that describes the work to be done and rates of what machines that I write in each time along with trucking of each machine or trip charges, etc. and thngs like that, pretty simple, but stamped on the forms theres things in wirting that state the liability, collection, billing info and statement dates of so many days before interest starts and the annual interst rate, simple things like that, you can also get creative and add things that covers your butt as well, remember if its in writing and they sign its basically legal, but an attorney can help witht that, its their job.
You also need legal help to tell you how to fill it out beforehand whats needed and not needed on the form, they will tell you to jot down this but never that, they will tell you how specific it needs to be in your state.
My customers wanted to sign the forms, it was simple and easy and they had a copy to keep that stated an amount per hour or whatever I was going to charge them for, all spelled out and it gave them peace of mind that they'd get billed what I told them I would, it covers both parties to a certain extent and thats what they wanted, nobody had done it before in my area and I was the first. Now for the real kicker I never saw coming using forms, no crook will sign it, crook meaning anyone who won't pay the bill and your fighting with now, they'll never sign anything, they know it makes argueing almost impossible and legally they agreed so their stuck and they know it, everyone I'd figure I'd have problems collecting from refused to sign and hired someone else, guess what, now my competition is trying to collect instead of me. The other side effect is all the crooks stopped calling period, they know I'll require them to sign so they don't even call anymore, so thats a perk as well I don't need to even deal with any of them anymore.
Do yourself the largest favor you'll ever do and get some forms and get signatures and do it today, it might not eliminate all problems but most of them it will the other thing is if you need to go to court you have something on your side as evidence, also take pictures as you go document everything so you have proof of whats being done along with a daily log book you keep that states what you do and the hours on the machines you ran that day or how many hours your at the job that day, however you bill, you need something in writing to protect yourself later on, before, during , and after pictures I use a digital camera and when I get paid I don't print them out, if I don't get paid I print them out and put them in a file.
I have forms printed at a local printer for a few pennies a copy, two pages that write through, after signatures you keep the front one and the customer keeps the second one, they just tear apart and have a carbon type prinitng on the back of the first one, just don't wirte on more than one at a time and your good to go. I don't do work anymore unless I have a form with signatures, I did one last fall without and I did have problems, it was my own mistake and I should have but it wasn't that big a job and I didn't take the time to have the forms signed, my own fault, after this I don't care if its only a 100 dollar job, eveyone signs, otherwise I haven't had any problems with anyone since the forms other than the one guy who came through after the attorney called him, whiich is still good in my opinion, basically its taken collection out of the equation for me completely, for now anyhow and the worry to go with it. If I can help you any more let me know, I can personall message you specifics if you need them on more things if you want and answer any questions you have about the forms and what I did.