Work /
I'm retired teacher, age 69 - I want to teach English in Poland voluntarily, in return for Polish language [18]
Do you have enough funds to support yourself for a period of time while you build up clients? If so, you could get your own company established while you are taking Polish lessons and slowly build you client list. The benefit of starting your own company - first 2 years ZUS (social, medical) costs are substantially less (in my case, from what I recall 254PLN for first 2 years, after that 900+). I would also suggest if you do come over to get a good accountant ASAP. I pay about 60 PLN/month for this service - money well spent, believe me.
If this is what you want to do, and you have some funds available to give it a go, go for it. Note: I am assuming that you are in relatively good health.