There's nothing wrong with starting a character and playing them for a bit - it's very easy to level up if you change your mind.
With that in mind, you technically can solo any character up to a certain point - some further than others as mentioned. But, you will probably end up having to farm money to buy gear or get support. Personally, I think you miss out on the whole custom content experience if you're not actually obtaining the gear yourself or with friends.
Also, some guilds accept solo players and I've heard some others don't box at all - that's one thing to keep in mind.
Personally, I started playing a rogue to group with friends. I had to start over and focus more on a tank when they left the server. I ended up making my SK and I solo a lot on him but only after getting his epic weapons. Again, going solo you'd have to find some way to complete them and some of the epic bosses are a challenge, if not impossible to solo at first. There's a lot of friendly people who might be able to help and if you prefer to pay your way through it, that always works. Boxing is always more efficient and that's the only reason I do it (because I have limited time).
In the end, find something you like to play - that's really all that matters. I'm playing a wizard now and leveling him solo really didn't take long at all and it was a lot less masochistic than it would be elsewhere. I actually enjoyed it more than I initially thought. To each their own, I guess

Tython