The NCAA just dropped two years worth of Transfer Portal data. While the portal sometimes works out for kids, the data bears out what we all probably suspected and your grandma definitely told you growing up, "the grass isn't always greener on the other side". In fact, for a surprisingly high number of kids, there's no grass on the other side at all.
The NCAA's webpage allows you to see the data for particular sports and for FBS football, that data isn't pretty at all. For FCS transfers, however, that data is downright fubugly. Only 27% of FCS players going into the portal end up with a scholarship at any level on the other side. That's still 2.5x better than the results for FCS walk-ons (11%).