Be prepared to do some work when you do acquire one. If it's been left unpainted and mostly unrun, it will need cleaning and lubing at the very least. If it's been run heavily, there may be wear problems. Broken or missing parts will be difficult or next to impossible to find.
For the most part, older imported brass locos would be considered mediocre to poor runners today. There are some exceptions. And some will have been reworked for better running.
Unless you enjoy these types of projects, or are seeking a prototype only made in brass, you will generally do much better with a modern plastic/die cast steamer. Less money, better performance.
All the above said, I was able to get a Ken Kidder HOn3 Porter 0-4-0T from eBay for less than $50 last summer. To make it run well, I will have to remotor/regear and tune. I also need to add details and paint. Won't be a cheap loco when I'm done, but it's a fun project. Luckily, I have found/saved web sites and information from others who have worked on this particular loco.
yours in project work