Coachinghopeful, let me tell you first of all to secure a teaching position. Coaching is a great experience and something that I think you will definitely enjoy. However, along with coaching comes the responsibility of teaching. You will be hired, and make the majority of you income from being a teacher and not a coach. Once you have landed a teaching position, then I would recommend that you approach the football coach on staff and ask to help out with the freshman, even if he cannot afford to pay you the first year (the pay is not that much anyway). But as a teacher asking, and just some dude walking in off the street, the coach is more inclined to take you serious and give you a shot. Once you get your foot in the door, then your coaching ability will take over and will determine your success.
The other reason I'm telling you to become and secure a teaching position, is because no matter how good of a coach you are, you will get fired one day. But if you are an effective teacher and educator then you will always be able to feed your family. I hope this helps.