I wouldn't work on someone else's project for "many days" for free. I strongly suspect most other candidates wouldn't either. If you start paying them for their work, then it seems the decision to employ has been made and the interview is in actuality over.
If you keep someone at work for this long, you should pay them at contract rates.
I would really like this as an option. If I wake up tomorrow and have no job, it would be neat if there were companies out there willing to pay me contracting rates for a few days, because it would let me pay my bills.
this is a complete mind shift for the process. Step 1, people currently employeed and happy with their job get permission to work from anywhere. i.e. a Self Contained Tech Worker. I work from any coffee shop I want to, my employeer is happy with my work. Step 2. I start crashing offices and working else where, still working for my current employeer. They don't care where I work, coffee shop, or some other office. Step 3. Over time as I work at new places I'll get to know new people. Leads to my next job when I'm looking for a switch.
