As noted by other posters, it is a little difficult to give you a specific answer to a pretty general question. But, I did a quick search of UT area condos (using 78705 & 78751 zips as search criteria) that sold since April 1, 2010 with no more than 500 SF.
Sold $/SF ranged from $192.89 for a 394 SF condo at 3000 Guadalupe to $270.00 for a 400 SF condo at 2206 Nueces.
Of course this does not take into account any HOA fees, special assessments, parking or ease of finding tenants - all critical info for investment properties, especially around UT.
My company specializes in UT housing and I'll be glad to give you more specific info if you want to contact me directly at firstname.lastname@example.org, 512/626-9885
Hope this info is useful.