Back in 2004 when I finished my MSc in England, I was immediately offered a PhD position with scholarship in the same lab by my own supervisor, but because I was non-EU student I still needed to pay the remaining tuition fee and self-fund myself for living expenses. My kind supervisor talked to his collaborators and one of them offered me a position in Giessen, Germany without any salary for the first year. I moved there, registered and started the lab work but I quit after just three months. If you search my name you can still find my info on their website. I admit that I still regret my decision although I am an assistant professor right now. If I stayed in that group, that had articles in Science and Nature, I would have had a better scientific future.
I quit because of many reasons and I thought I had made the best decision at the time. It was really difficult for my family to send money to me because I come from a developing country and the exchange rate to Euro was/is crazy. Besides, I didn't speak German to be able to work part-time in the town, unlike England. Anyway, shortly after my registration I was offered a job at a company, and I thought 'why live a difficult life when I can earn money?'. During my work in the company, I developed more interest in pursuing academic career. After 2 years I quit and found another PhD position with scholarship, but sadly, nowhere near those high-profile labs in Germany or UK.
My suggestion to you: if you think you have enough money to support yourself in that lab and you might land in a better place, take the job. Otherwise you will spend the rest of your life regretting it.