Hi Frank, welcome to the café.
I am sure you will find the answers to many of your questions if you searched around on the forum a bit. Your situation is similar to so many others that come to the Café.
In a nutshell, some answers....
-While nothing is impossible, it is highly unlikely that you will have any job secured before coming to Spain. Unless, of course, you come here on a scouting mission first, line up interviews, score jobs then return to the States before the fall season kicks in.
-As an American, you can be in Spain legally for 3 months on a tourist visa which is not legal to work with. I don't advocate doing anything illegal or anything you aren't comfortable with. However, there are many Americans in your same situation here and working under the table. It's not the most secure way of working.
-If you decided to go with a certification program, a few of the programs here in Madrid, if not all, will help you find housing and/or negotiate rental agreements for you.
Hope some of those responses help. I highly encourage you to sit back with a nice cup of coffee and spend a few hours searching this forum and reading the articles posted on our main page. Many of the questions you ask have been addressed time and again.
Good luck!
-Rebecca