In reply to Professor Bunsen:
Some factors to take into account -
1. How big is the room it will be used in? Audience size / distance from screen. what screen will you use?
2. Will the room always be darkened when you show images? If not you need a brighter (more expensive) projector....
3. How detailed do you want the images? 4k resolution will cost you....
4. Are you just projecting still images or will you also want to show movies? In which case you will likely need separate speakers.
5. I presume you will be sending images to the projector from a laptop. What connections does the laptop have, what connections does the projector need?
6. Buy a spare bulb and learn how to change it. Sods law says that the bulb will burn out at the most inconvenient time possible.
Good luck.
Paul