Has it slowed down on the teaching front? I have had a hard time finding anything.
Non-EU teachers are very undesirable at the minute to be honest - too much hassle and paperwork to hire them. I only know two schools in Poznan willing to bother with it!
Average starting pay?
Warsaw - 50zl/hour. Other major cities - 40zl/hour. Small places - 25zl/hour.
Does the pay increase over time (if you are worth it)?
Nope. You will find that you can negotiate up to a set point (for instance, in Poznan, 70zl an hour is the most you'll get from any school whatsoever, and all but two schools don't pay anything near that) and no more. I've got exactly this problem at the minute - I keep being offered work, but nothing over 60zl an hour from schools. It's not bad money at all, but apart from rises for inflation, you can hit this very quickly. It's why most people here long term tend to go completely freelance.
Do people ever attempt to make a career out of it?
People do, but they tend to gravitate towards public institutions. It depends really - but if you're looking for the serious money, Europe in general isn't the place to go.
What happens in the summer when school is out?
You starve. I have work all through the summer (ah, the joys of being freelance) - but many teachers don't.
Can TESL eventually provide other opportunities if you speak both polish and english?
If things don't work out, how difficult is it to find employment speaking both languages, decent employment?
In all honesty, if they consider you Polish, then you'll struggle without a Masters degree. Any decent job will require it as a de facto standard for a Pole. Of course, you can find other things - but it's very difficult to do so.
Is it better to take a course in Poland rather than taking it here?
Generally, it's best to be on the ground.
I heard that some schools provide housing, I wouldn't want to share a flat with anyone so would the school pay for part of my rent if I chose to live somewhere else (assuming they did offer a place to live to begin with)?
Schools that do that tend to be located in backwater places. As for the second part of your question - it's all up for negotiation. Very often, school directors simply have the use of a flat from friends. But don't expect accommodation to be included at all.
Does the school pay for health benefits, does it come out of your pay, or do you have to go out and get it on your own?
Most schools won't pay for it.
How much are avg living expenses in the avg sized city, including food, rent, internet etc.?
In Poznan a week -
food - 100zl
rent - 250zl (for a studio apartment about 20-30sqm)
internet - 60zl
public transport - 20zl
utilities - hmm...maybe 50-75zl a week?
I also have family in Poland, although they live near Rzeszow where I hear the ESL opportunities are slim to none.
I'd actually say the opposite - it's often very easy to find work in small cities. Natives are few and far between, and while you won't get paid much (25-35zl an hour), living costs are laughably low.