Making sure the plumbing and or heating company is licensed is the first place to start, but keep in mind not all areas require plumbing licenses,
If your town or county does not require plumbers and heating contractors to have a license, than they can't provide you with a license number.
The next item they should have is both liability insurance and workmen's compensation insurance.
You could be held liable for their injuries.
An insurance certificate is available on request.
You may also want to check with the BBB Better Business Bureau to see if there are any complaints.
A high price does not make a plumbing or heating contractor a crook.
I think you should be more concerned with a very low price, because this may be a scam or a fly by night contractor, here today and gone with your money tomorrow.
The cost of running a good professional company with high quality trained employees with trucks fully stocked to meet your plumbing and heating needs is very high.
In the end it's worth the cost, because companies that invest this kind of money in their business, plan on being around for a long time and will be there when you need them.
All that being said, run the problem by me first, it could save you some money and give you an idea of how serious the problem is.
I had a woman call me last year with a furnace problem.
Prior to her calling me she had a contractor work on her furnace.
She had already paid this contractor over $1,000.00 to solve the problem, but the problem came right back as soon as the contractor left.
She called me because she was frustrated and felt the contractor was just replacing parts at random hoping he would eventually replace the part that was causing the problem.
She described the problem to me over the phone and within 5 minutes I solved her problem, all she needed to have done was to clean or replace the flame sensor on the furnace.
When she told the contractor about the flame sensor, he said yes that is the next thing I was going to check, once he replaced the flame sensor the furnace worked fine and the problem was solved.
If she had called me first she may have saved over $1,000.00.
It is not my intention to second guess people that are out in the field, but to help you avoid the idiot that is going to cost you a lot of money either by their ignorance or their dishonest nature.
Please call me and run it by me first.
Also let me know if you had a good experience with your plumbing and heating contractor so I can add them to my list of quality plumbing contractors. I have no desire to list bad contractors in any way.
Please don't ask questions about price, it is not possible for me to say if a price is fair or not, or what a particular type of job should cost.
And please don't ask me if I think you were over charge for a job, it is impossible for me to know all the details, and it's none of my business.
I recommend getting a price up front.