On a DX body with a 1.5x crop factor, it will have an effective focal length of 28-52mm which is not very wide. You would be better suited to look for a used Sigma 10-20, Tokina 12-24 or Tamron 11-18 if a new one is not an option. Used these will go for about $400-$450 and new these will be around $500. There is not a "cheap" under $200 ultra wide on the market. The full frame Sigma 12-24 and Nikon ultra wides will most likely be out of the question as these are even more expensive.
If you are not aware, the D50 is a DX body so you will have the to figure the crop factor (1.5 times the listed focal length on the lens) when making lens choices. On a FX or full frame you will have the same focal length as 35mm film SLRs (no crop factor). That is why a 28-200 lens that was popular as a walk around lens lens on a film camera is not very effective on a DX body as the widest focal length will be 42mm on the DX body. That is why most DX lenses start at 18mm (27mm film equivalent).
You should be very happy with the Tokina. I compared both the Tokina and the Sigma when I bought my ultra wide. I liked the constant aperture of the Tokina but the extra two mm on the wide end of the Sigma was the deciding factor for me. The variable aperture of the Sigma wasn't a negative as I usually shoot my landscapes at f/11-f/16 on a tripod. You will probably find that you will get more use out of this lens than you ever thought you would and you'll want to take it with you, wherever you go. The nice thing is that it's small enough that you can - it takes up very little space in your bag.