Solo as a rookie is a bad idea for many reasons.
#1 - going with other rafters is the best way to learn. You don't need to pay for training, you just need to hook up with some veteran rafters who will teach you the ropes. Look for a local rafting club to do trips with. That's how I learned.
#2 - most rivers require certain equipment for multi-day trips. Groover, fire pan, first aide, rescue, repair, spare oar, etc. That's a lot of stuff to carry on a mini cat.
#3 - it's very unsafe. Especially on an unfamiliar river. I have been rafting for 17 years and I've never done a solo. I'd like to do one someday, but only on a river I know very well, and where help is easier to get.
"We are all visitors to this time, this place. We are just passing through. Our purpose here is to observe, to learn, to grow, to love....and then we return home."
Australian Aboriginal Proverb