Wow, so much advice. In fact it's all pretty good. As MAB says there's a ton of sacrifice to make it happen. I still remember sleeping in my car the first few nights in town while I waited for my session checks to clear the union. but I came to stay. For what it's worth your demos should be professional quality. I've heard some vocal and guitar demos that were professional quality but most of the time not so much. There are several of us here who do professional quality demos with A team players and professional studios. It isn't all that cheap but then it's not all that expensive either.

That first impression is always the most important one.