first and foremost, you can NEVER have too much space to work with. if you buy small, you stay small ( so to speak ) You can’t add to it. If you go big, and you don’t use the space right away, that’s ok, you can fall back on it later.
 
Lots of different things make up a good cart. First is manufacturing, how well it’s built, how long it’s going to last, what grade metal is used. Warranty is the next hurdle.
 
What is your budget on buying a cart ? Are you thinking of going with new or used ? 
 
Roadfood has a great search query for carts. You can/will find alot of great threads on here about cart discussions.  Not bashing, just saying… I was once new on here too 😀 We all gotta start somewhere.
 
What are you thinking of selling on the cart ?