Dude, if you are a skilled welder, go for it. Setup a good cheap truck with a flatbed and install your welding rig an whatever else you need and freakin go for it. I think you will be surprised at how easy it is to stay busy.
If I could give any advice though. Try to get the business going and making money before you spend to much on your tools....(Fancy diesel dually truck). I say that because that is a mistake I see around here. People go purchase a brand new ford f350 or 450 and out fit it and end up with a 1500$ car payment

. Since your a welder already you know exactly what you need for welding equipment and are likely not to over spend on something you don't need in that department.
Good Luck!
That’s some solid advice right there.
Being self-employed is very different than investing in a business. I would ask yourself; do you see yourself being a business owner or a wielder? That will help you focus on the scope of the work and help guide your choices.
When you invest in a business you are really hoping to build it up to either pass it on to another generation, generate sources of income while building appreciable assets or to eventually sell it for the capital return.
You will get more flexibility being self-employed than you would working for someone else and can earn a nice living or return if you build the business and sell it. You will be working for your clients, they are really the boss. But I would think of it like you’re just buying yourself a job. It’s a job in which you happen to own all or a portion of all the assets and customer lists; but it's a job. In the type of job your planning on buying, you are also the only income generator. If your good at what you do and if there is a market for that type of thing where you live, you will quickly outgrow your ability to take on additional orders. This is the greatest limiting factor of this plan. You can try to keep up yourself but eventually you will have to decide what you want to do, limit customers and income or expand. In order to expand (if you choose to), you will have become either an employer or outsource the work for a vig. All this stuff is business management – not wielding.
I would certainly hire a tax accountant from the start but understand that they are limited in expertise in control accounting. This may become more important to you as you grow your business. Use the accountant to set you down the right path to limit your tax bill and keep you out of the clink. Don't stress too much about paying taxes, it means that your making money. I would also consult with an attorney who's expertiese is in corporate law - these two folks are going to be your closest advisers and will keep you out of trouble.
I would recomend limiting your risk by making only reasonable capital expenditures that you need to in order make the business work vs what you would want to have in your personal life. I would have the best working weilding equipment that I could resonable afford if it will help the end product. Look for the deals, keep your equipment maintained and clean and you'll be all set. Let your work/finished product / service do the bragging - not expensive equipment.
I had an electriction and a plumber on call who both purchased brand new trucks in the same year. They were proud of those trucks but all I could think about was that I was paying for them as a client. Everytime they handed me a bill they did so with a toothy grin. Many people think that buying a big fancy truck is good advertising. Advertise digitally - it's more effective in most cases. Most self employeed folks usually end up building all the business that they can handle by word of mouth anyway. If you want a fancy vehicle look - a cleaned up and wrapped used vehicle will look like a $80k truck. When you think that you made enough money to make additional investments into the business, wait until you know for sure. Endeavor to skip the ego purchases in business and buy your wife and kids something nice instead. Life screams at you and will let you know when you absolutely have to spend money (could be the loss of business due to poor equipment, loss of opportunity, loss of efficiency), but every capital purchase spent on the business should be generating more $ and generating more clients.