I'm a little different and in a different field than most, but I'll share from my experience in my business and my experience helping my son Chris get started in his concrete cleaning business.
1) The biggest challenge on the concrete side was taking on jobs we were unfamiliar with and trying to do them without reaching out for advice from those more experienced. Some examples would be bidding 400 on a paint stripe removal at a tire shop that took 18 hours, seeing stripes from the surface cleaner and continuing to do the job trying everything that made sense without calling someone who could help me fix it immediately and taking on complicated jobs that could have been done much easier if I had just called in advance.
Our market is the same as Ron's and Scott's. We clean a lot of the same things. So Ron and Scott are both on speed dial and I call them regularly for help when we are doing a new type of job we've never done before. In five minutes they can tell me things that save us hours. That is the value of experience. As time goes by we need to call less and less but still almost weekly Chris will get a call to clean something he's never cleaned before and no matter how simple it seems on it's face, I always tell him to call Ron or Scott first just to make sure there isn't something they can add to make it go smoother.
2) The first mistake I made was not being on the boards and not knowing about guys like Russ, Paul, Jerry and others who know everything about troubleshooting equipment and instead paying full retail for my first machine (around $9k just for the skid). I wanted something with a warranty because I was unfamiliar with the equipment, but little did I know, warranties on skids don't cover very much. If I had bought a used one to get my feet wet I could have utilized more than $5k in savings for marketing materials.
There is definitely a value in new skids, that value comes when you have enough business that your time is full and it costs more in time to troubleshoot than you have available.
We also made the mistake of not knowing the market and wasting a lot of time on unqualified leads. Once Ron directed us to where the bullseye was, everything changed.
3) Three things I would do differently:
a) I would bank every dime to pay cash for every upgrade instead of relying on a credit card or financing that eats up too much of your profit in interest payments.
b) I would determine, from other veterans in my field what my target market is and zero ALL my brochures, web pages, and other marketing in on that segment. Once established and making money from those, then I would have the luxury of spending money on fringe areas of pressure washing.
c) I would set up regular customer contact on a monthly basis to make sure I don't lose accounts because I failed to build a personal relationship with the customers.
Organization:
a) I would have set up an LLC instead of and SCorp for tax simplification.
b) I would have set up an ironclad system of scheduling from the beginning instead of relying on scratch notes and memory.
Advice:
Don't pay any attention to business school propaganda, self help junk, inspirational seminars, and other such nonsense.
Get out there and take all the work you can get without fear.
Rely on the experienced guys to help you when you take on something new.
Don't be afraid of the big jobs. Take them and do them with every ounce of your energy.
Latch on to someone who succeeds at the level you would like to succeed at and learn from them. You won't need any motivational instruction once you see that money dropping in your bank account on a regular basis. Leave that for the guys who are too lazy or proud to do what they have to do and watch them branch off into every other shiny object business opportunity they see.
Use some common sense when choosing a mentor. If your mentor says one thing on the boards and another on the phone, he is a liar and will bring you down just like what has happened with some "specialty" cleaners who are now selling their pumped up equipment and going out of business because they couldn't make any money with it and listened to an idiot.
If your mentor asks you to pay for meals, lodging, etc, he is broke. Run away. Unless you want to end up broke too.
Read the boards, use the search function, use your brain and latch onto someone who can guide you through getting your business started.
After that it is up to you to determine if you have the drive to make this a lifetime profession that you can pass down to your kids and grandkids.
Hope that helps.