Hi andreac and welcome to the forum. Yes there is a demand for TEFL teachers especially in Madrid and Barcelona (or other large cities). There is a useful page on this site about teaching English in Spain.
I’m not familiar with TEFL training in Spain as I did mine many years ago in England…so can’t help you there.
Most schools only offer part time positions so you may have to do a couple of part time positions, and look for individual students to teach them in their home (or your home - be careful!) to make ends meet. It seems quite competitive however so make sure your CV is up to date and clear. It also helps if you can speak Spanish!
There are pitfalls and some schools won’t offer contracts or only pay for ‘self-employed’ teachers on short term contracts (which happens in England too!) - I think its so that they don’t get ‘stuck’ with unsuitable teachers. You can always ask on here if you are in doubt about a particular offer…..or course.
I’m happy teaching English using Skype video calls. You have to do a lot of emailing to prepare your students for the next online meeting, but I’m not complaining 😊
Do some research before before taking the plunge and I hope some other teachers on here can give you some guidance, so you can make an informed decision.
keep in touch, lioness