if i provide wireframes, user journey and flat psd design, can you quantify 'not too much'? avoiding to pay someone to validate the idea would be ideal though.
I might just buy an airbnb clone to test it out, why is no one suggesting it, does it not work at all or is it just bad practice from a tech perspective but could solve my case?
It's hard to clarify not-too-much as I've been out of the freelance game for a long time. I think your best bet would be to come up with a design mockup, and a good chunk of information about how you want the site to work, UX, user flow, that kind of thing, then approach some developer circles and see what offers etc. you get.
Places like Ask HN, or Reddit's /r/webdev would be good places to post a plan and ask for quotes maybe?
If you think this is a solid business idea though, I wouldn't try and do it on the cheap or bodge it on to a framework it doesn't fit with, otherwise you'll be worse off down the line when people have already had a bad taste of your brand and don't come back.
IMO if you took this kind of approach, you'd learn to make up a design using a framework like Bootstrap, then pay someone to either code something basic (on a framework like Laravel for a good developer it shouldn't take much time at all for a user system with listings and a search) and use your design. It's an expense, but not too much, and it'd make or break the idea IMO.