Your options are going to be affected primarily by the amount of coin you are comfortable spending and whether or not you have access to someone who can work with you to tell you what's a good horn and what's a bad one.
First, not all horns are equal... even if they came off the same assembly line within the same 15 minute period of time. Some of the apparently most insignificant things can have enormous effects on how a horn responds and how it plays... whether it has accurate intonation or not. This is true for new horns of ANY "quality/price" level (including custom-built) and old horns (which may also have had quite a bit of repair work performed on them over the years).
Second, although it is possible to buy used off of... say.... Ebay..... you really are taking a great risk (or several risks). There is the honesty of the seller, the accuracy of the description, AND the playing characteristics of the instrument... none of which you are likely to know ahead of time.
Third, as a relative beginner there are many playing characteristics that you may be blind to.... the impedance (commonly called "resistance"), valve action (there is smooth and there is smooooooth), and the effect of different mouthpieces (not all horns work well with all mouthpieces and all players).
Your best bet is to remember that you USUALLY "get what you pay for", "if it's too good to be true then it likely isn't true", and "it's always buyer beware". Find a shop that has a solid reputation for honest that sells used horns and find someone who is an experienced player that's willing to go with you to help make the selection. It also helps if the shop has in-house repair capability... they will more likely have been able to recondition a used horn and are less likely to be selling some of the "cheap junk" that's been finding it's way across the Pacific in recent years. (Not all Asian production is cheap junk... but MOST still is).
Here's a superb resource to read up on:
The Trumpet Gearhead
Trumpets are like shoes... what fits me doesn't necessarily fit you.
And.... welcome to the world of trumpet!