Right now you can rent a reasonably nice all-utilities-included 2 bedroom apartment near ASU in Tempe for around 800$/month, or a cheaper efficiency for several hundred dollars less.
Any condo/townhouse in Tempe is going to work out to around or a bit above that in cost once you figure in HOA, maintenance, and mortgage (assuming a low down payment). With the local real estate market involved in a fairly unprecedented upheaval of foreclosure (-especially- in condo's/townhomes) it's hard for me to recommend buying right now given your short-term plans. Tempe's condo prices have been a bit stickier then they should be given the demographics and historical prices. Look at values pre-bubble on these condo's, compared with values today. You can draw your own conclusions (all real estate is -very- local), but I believe most of these units in Tempe are still 10-30% overpriced. If you do purchase one, try to shoot for pricing in line with what the unit would have sold for pre-2001-2002 (pre-bubble), and be very careful not to end up in a condo with a large number of oncoming or current foreclosures (that can shut down future FHA financing possibilities for potential buyers, and has serious negative repercussions on the property's value). Have your realtor do a bit of research to ensure you wont be surrounded by 45 people who bought in 2006-2008 and haven't made payments on their 100k underwater condo in 12 months. Also, condo's with very few occupied units have issues maintaining the property thanks to a lack of collected HOA fees.
If you intended to own the property a -good- long time it is probably a fine investment and costs should be close to equivalent rental prices (IE, you can ride out any shorter term fall in pricing comfortably). If you intend to sell in 4 years it's hard to recommend a condo/townhouse at the present time.
My recommendation if you -do- go this direction would be to look specifically at townhouses rather than condo's. There are quite a few stylish townhouses that fit your under 100k umbrella, and some that are actually bigger then you are asking for (3 bedrooms for instance). Take, for example, the townhouses on the east side of Mill Ave between southern ave and baseline. Stylish two-stories, situated in blocks of four townhouses with nice shared green lawns, reasonable pricing (one nice 3 bedroom recently showed up for 90k), 2 miles from ASU (easy to bike - use college ave) and it's on a direct bus route. They are rarely vacant (easy rentals) and have enough curb appeal to sell relatively quickly when they come up on market (assuming they are reasonably priced for the market, of course). These would make a great college pad, with room to grow if you decided to stay and start a family, and should be easily re-marketed down the road.
That's my two cents...