Ha ha....good questions!
Normally people using HelpX are travelling between places as part of a trip. I never had someone come specifically for my project.....more as a series of projects to pass through and gain experience.
My lifestyle and work is physically demanding and I generally only take people who are 'in shape' so to speak.
It doesnt matter what experience you have or don't have, if your physical capable and are able I'm happy to take you.
At the end if the day it's about exchanging skills - I will teach you self sufficient gardening, forest management, goat herding, how to build in stone etc. There's no expectation of your skills, just the willingness to develop and learn.
This goes both ways. I am always on the look out for volunteers that have skills I want to gain too.
If someone decides they don't want to stay or help anymore there are many options out. Firstly the exchange is based on bed&board swapped for work.
If you don't want to work, the accomodation is available for rental as one example.
Also 'work' can be very loose.....if someone was to cook my evening meal and clean my kitchen I would be happy with this exchange. This would allow me to focus on work and be much more productive, I would be cool with that.
I also have loads of friends living close by that have a multitude of different projects. If a volunteer decided they didn't want to continue here, I am in a great possition to find them a more suitable place to be.
So, what's stoping you?