To both you and raphinou and others battling with the same questions, I cannot recommend Rob Walling's work enough.
His blog [0], book [1] and podcast [2] address the exact concerns any new software bootstrapper faces.
He also runs the Micropreneur Academy, but I don't have any direct experience of that.
He also organises Microconf, and I really recommend watching his talk from last year - http://www.microconf.com/videos-2012.html
The sheer number of products he has built, launched, acquired - both successes and failures - over the years gives all of his advice a lot of weight.
[0] http://www.softwarebyrob.com/
[1] http://www.startupbook.net/
[2] http://www.startupsfortherestofus.com/
PS I don't have any affiliation with Rob. I'm just really grateful for all his excellent work.