When I first came to China in 2004 the ESL certificate (as I call it) as bot a real requirement, but it has become that way over the last few years. i think there are more options in the bigger cities like Shanghai or Beijing for getting jobs but in Kunming they seem to be real picky these days, sometimes even asking only for AM degrees. They are not willing to pay more for those MA teachers, but they seem to want those as it makes the school better. Usually you can get the post with a BA in the end. Also one will need reference letters at any of the colleges or Universities here. Some people here may say "oh you don't really, and you don't really need the ESL certificate" but I am assure you that you will. I am not sure about the language training centers and there may be flexibility there. Or maybe not. There can always be some exception to the rule, but 90% of the time you will need at least a BA, a ESL certificate (I got mine through a Canadian based company in Beijing and it was based on teaching experience in the classroom and a few tasks, but it cost nothing, but that company is not in one horse town Kunming).
I worked PT at Robert's Language School a while back and it was pretty cool. I was not one of their regular teachers and so had some flexibilty with what I did and it was good, since teaching kids requires a period of sorting out whether you can do it or not. It was all kids and at first terrified me but I survived and the little guys and gals seemed to like me. The staff there were all cool and I think there are two schools if you want to that route. But I do not know about all of these language schools here. Not colleges or Universities. I had an offer from another one located on Wen HUa Xiang once. I was told "we have a wonderful job offering, please come now to get it!!!" and when I got there the wonderful job was in Ge Jiu, in the remote south of Yunnan. Their idea of wonderful and mine did not seem to mess.
But one thing tallamerican brought up that was not too addressed here, or at all, was the issue with his age, of 59.
It can be an issue, though I know or one teacher now who is 65 and another who is maybe 62 and working still. The 62 year old guy has a Phd and that probably helps. The 65 year old Yank was sweating the last few years but seems to be getting his contract renewed with little trouble. I am 55 and it is a problem I guess. Again, in 2004 there were teachers pushing 70 all over the place. Maybe some them were dying off in the middle of contracts or something.
Is your wife Chinese? I am sorry to ask. I assume she is because she is retiring here in Kunming. Not my business but it can affect decisions you make. You can, of course, always do the marriage "visa" (not really a visa) for your residence permit and take it easy man. I am telling you, at the age of 59 to step into teaching Chinese college students (I hope you would not consider high school or middle) is not what you may be thinking. Almost better to just do kids! Well, I won't go into that.
An option may be teaching online now. This seems to be a booming little industry. places like kukuspeak have teachers teach via a "stable internet connection" (this is China, but I know people who have done it from school PCs). I do not think there is any issue with age or even degrees. You will not make as much maybe as if you were working a school, but you can bring in some money. I think too you can retire early ay 62 if you wanted do (with some loss of payments, but it can stretch in China) and that info in online or at an embassy.
You can PM me if you want some support man. There might be a couple options on your plate.
Bill