If you want a space for your students then buying and renting land will probably be required. Depending on your students, you may want to consider other options such as OpenSim such as Jokaydia grid and Kitely. I'm sure some other people in have more to add!
Maybe this isn't the place for this, but I thought I would mention that UMass Boston (University of Massachusetts Boston) has facilities in Second Life that seem to rarely be used. So people can use this location as well for MOOC meetings.
I am interested in making a place for my students, but am not sure where to begin.
Do I need to actually buy land?
Frankly, I wouldn't buy land yet, until you're more used to Second Life (or wherever you end up). Buying is expensive. I'd recommend renting.
Myself, when I bring students into Second Life, we drift. I'm more interested in finding art/design related installations and museums than having them begin building immediately.
When/If I do want them to build, I generally find an educational sandbox using the search function in Second Life. I'm strongly considering bringing students into one of the OpenSim variants that kae mentioned (OpenGrid, Kitely, etc), instead, so I can experiment with having students build.
I am conflicted about second life. Nice concept, but I really don't want to spend a lot of money on land (or time in development) and have the service go down. Unlike HTTP protocols and HTML where you can run on any server (so if one provider goes down, you can run your own), second life is one company that controls the entire thing. It's too much of a money and time commitment for my tastes :)
I tell my students all the time if they ask hesitantly if they can ask a question, that "there are no stupid questions, if you as one you want to know, there are only stupid answers and I am on the rough end of this exchange!"
As for me Second Life doesn't interest me much (can't kill stuff) but FRCC with Kae's help, and my Introduction to Chicano Studies class, did create a Day of the Dead Island, they designed it. Kae and I thought we knew how it should look, but the students had other ideas. Theirs was better. We took the students into in in pre-designed avatars (time limit on our classes) and they got to walk around in what they made and Kae would make real-time changes, they even managed to get all the way around and then together for a group picture, I will post it to the Image show. I Know I have it somewhere!