I am fine with asking for candidates to work as a 1099 for a month if you pay them the standard 1099 contractor rate, which is almost invariably more than 2x their FTE rate. I am not fine with the industry norm of paying people their eventual FTE salary on a 1099 basis; that's a scam.

I think it's pretty dumb to do that, though, because most software developers can't take a month off of work from their current job to see if they're a fit for your company, and none of them will put their health insurance in jeopardy to do that.

I also think it's pretty silly to design a process that deliberately demands a month of time to make a decision that could be made effectively in a week.

Yeah last time I did it, it was just a week. And I got my full contract rate (which is about double as you suggest). It went well; got an offer.

Its not usually that hard for a contractor to take the time off; they're on their own time already.

That strikes me as a very costly way to build a team. Independent contractors are expensive; they know, better than most other developers, what their time is worth.

Microsoft, of course, interns college juniors for 90 days as a summer job. Less costly I imagine per hour, but apparently working for them.