For starters it would be wise to do the research for yourself. I am not going to be your babysitter and do the research for you so for starters I will post this one link and only link: http://www.payscale....d_States/Salary. The rest is up to you. Now you need to do a bit more digging as well into the stability of the field, as well as make strong considerations and preparations to return to your previous job as a plumber.
You think I have not done any research on the topic? I have only been investigating it for the last 5 years while I been in school! GIS pay varies dramatically by region. For example, entry level is about 30,000 a year in Boise, ID. Another problem is that many local government either have no GIS job category or that category is really a low pay scale. This means that many GIS professional working in local government are officially classified under IT or Buisness Analyst. This also means that it is often hard to determine what people working in the field make. In CA for example, you can see the pay of every single state government employee. Clearly, there are more people in GIS than a search for the title returns on transparent California. This is because they are under IT. Infact, you can find my professor who is head of the GIS department at a local city, but he is listed as IT manager. He makes 130,000, but you can't find that out by searching for GIS. Their GIS tops out at 70,000, so they had to move him to the IT classification.
The idea that plumbing is somehow more stable and I should return to that is both wrong, negative, and rude. Too much maple syrup last night? I am a new construction plumber. During the recession I did not work a single day in 2 years. How is that stable? That is why I went into GIS. My construction background makes me the ideal candidate for any sort of GIS involving utilities and infrastructure. Aside from that I with my physical geography degree I could also work as an environmental scientist, water conservation/resource specialist, and so on. In fact I have standing job offer to start a GIS department for a small city and assist the environmental scientist too. I just do not want to relocate to where the job is, but it would be better than plumbing.
The website linked to says 18 dollars an hour for a GIS tech. Nobody I know from undergrad is only making 18 an hour. Everyone is making about 45,000 or more. Some who went into local government are making 52,000 or more to start. They do not even have a MS. My friend started at 48,000. Now with three years experience makes 70,000 + . However, most these people are in public sector and all are in CA. Heck, there was a job posted last week for an oil company in the middle of nowhere in Oklahoma, entry level no experience 75,000 with full benefits.