Noob question

Hello everyone,
I would like to approach this world by buying an 8 years old deshojo maple. I have a doubt : how much margin do I have to modify a bonsai of this age ? Or should I be "satisfied" only with maintenance? I mean trunk thickness, style, height etc. I have read several things on small guides but have not found an answer.
Excuse the silly question.

An 8 year old Japanese maple is bonsai is still fairly young, particularly if it was actually grown as a bonsai and is not a nursery tree that was just lifted from the growing bed. if the trunk is much more than 1 cm in diameter it is apt to be difficult to bend and change. However, these trees tend to bud back very strongly so long straight sections and can cut out and regrown. Branches are even easier. Smaller changes that will dramatically impact the image can be made on much older trees. If it is a price and has some features you like go for it and post a picture or two against a plain background it you want suggestions.

Agree with previous post. It will be your oyster to style once you purchase; the trick will be keeping it outside and alive, so don't spend too much on your first one. I recommend finding some local volunteer seedlings in your garden and potting them up in the spring, while they likely remain "stick in pot" style bonsai for a while, you will establish the horticultural skills required for potted life of a tree.