If you truly have no money, then you definitely do not want to try to modify the Rebel for real off-road use. It will cost you way more than trading it on something more appropriate, and it will still be inferior.
The Rebel is already capable of mild off-road use by a reasonably mature adult who understands the need to baby it. I ride mine in pastures, fields, farm roads, double tracks, and logging roads with no problems. I have even used it for herding cows. However, I ease over or around obstacles or move them. I do not go flying down these roads, or jump terraces, or other things that true dirt bikers love to do. The suspension won't take that, but it will handle dirt just fine at a reasonable pace by an experienced rider.
Everyone who has learned to ride on my Rebel has done so on dirt first, since it is softer, more forgiving, and not filled with other vehicles.
1999 Honda Rebel CMX250C
2003 Harley Sportster 883 Hugger
1998 Harley FXDWG Dyna Wide Glide
ALL IN! GO TIGERS!