Hi Bauluo,
I agree, it's a gamble! If I'm not mistaken, non-permanent would be legitimate and lawful as long as its within your land. If you don't own the land, I'm not sure about how it'd work. Don't take my word for granted, since I'm no expert on the topic
I guess the situation in Portugal is quite similar to that in Spain. If that's the case, there should be a lot of abandoned small villages, farms and barns. A lot of them are sold at a pretty low price, since the big expenditure comes with refurbishing. Maybe that's an option?
I'm currently living in a suburban apartment, however the permaculture project I hope to carry out includes non-permanent bioconstruction structures. I think it'll be fine as long as there are no troublesome neighbours, heh
Regards,