Research the columbian red tail boa and see if it is something you would be willing to take on. See how big it gets, what it eats (size wise etc) and what husbandry you need for it. Don't just go for it because it is a good deal without doing some good research first. There isn't a guide on what you should have for your first snake, everyone likes different things. If you think this is the snake for you then you could go for it. I like BP's as a personal preference but I wouldn't simply discard other breeds of snake for other people.

I do prefer going for the younger snakes as you grow and learn with them but there is no harm in going for an adult if you feel ready for that.

I found this on google where an owner said she would not recommend for a beginner as they are classed as medium to hard experience level:

"because of their size and care needs, I wouldn’t recommend them to people without at least some experience handling large reptiles, and I wouldn’t dream of recommending them to beginners. I have owned five of them"

And more info I found off the same person about Columbian red tail boas:

Size: Males average between 5-8 feet, females average between 7-10, though I have had females that have been 11-12 feet in length. Keep in mind that a snake that large is very awkward to handle, and can be fifty plus pounds. If you don’t have someone to help you handle the snake as it grows; I would suggest getting a male. It simply isn’t safe to handle any constrictor over eight feet long without another person around, no matter how docile your snake may be. Accidents can and do happen.

Feeding: Feed one appropriately sized rodent weekly. The general rule of thumb is to feed a prey item that is roughly the same in diameter as the widest part of your snake’s body. They have a massive feeding instinct, so it is often best to offer food on tongs. They are capable of taking rats from the time they are babies, and some of the larger females do best with rabbits. PLEASE remember that with rats in particular, it is imperative to feed pre-killed or at least stunned rodents to your snake. NEVER offer a life rat. Rats are very intelligent animals that will fight back; and are quite capable of seriously injuring or even killing your snake.

Temperament: They are generally docile, but must be handled regularly throughout its life in order to make it as friendly as it can possibly be. Babies can be nippy when young, but usually grow out of that stage with frequent handling. Most of them are quite mild mannered, and are one of the best tempered larger constrictors. Please remember that you’ll need someone to help you if you handle any snake longer than six to eight feet long. They seem prone to being moody at times, (particularly the females, for whatever reason) and while not all; some of them will randomly decide that they don’t like certain people for no good reason. For example, my eleven foot female, Bella, loves everyone and is an exceptionally friendly snake, however she absolutely loathes my best friend’s brother. She will lunge at him if he so much as walks by her cage, God forbid he get near her when she is being handled. He has learned to give her a wide berth.

Lifespan: If well cared for; they can live 20+ years in captivity.

Caging requirements: As adults; they need a minimum cage size of 10 square feet. I generally keep my females in cages that are eight feet long by two feet wide by two feet deep, and my males in cages that are six feet long by two feet wide by two feet deep. They do grow pretty quickly, so be prepared to purchase several different cages for them. They seem to do best in closed top, front opening cages that keep the humidity in. If that isn’t practical and you use a typical tank with screen lid set up, try covering most if not all of the top with a towel or something similar to keep the humidity from escaping.

Heating/Humidity: The temperature gradient in the cage should be maintained with a basking spot of 95-97 degrees with an ambient (background) temperature in the low 80’s. This can be achieved by under-tank heating pads, heat lamps, or ceramic heat emitters. They are medium-high humidity snakes that should be kept with a large water dish for drinking and soaking, and should have their cage misted every other day or so, or depending on the substrate you use, up to twice daily.

Substrate: While there are plenty of options out there (repti-bark, aspen, cypress, paper towels, etc) mine have done best when kept on Eco-Earth substrate by Zoo-med. It is compressed coconut dirt that holds humidity very well, doesn’t need to be misted often, seems resistant to mold, is relatively cheap, looks great, and my snakes have all been healthier and better hydrated since I’ve been using it.

Have a read through and see what you think, personally I would say not for your first snake but who am I to dictate your personal choices