I purchased a plot of land in Morthal but I cant find Valdimar. Anyone know how to fix this?

Did you meet him when you purchased the land? Purchasing a plot of land does not automatically entitle you to a housecarl, only thanes get housecarls. And even if you have a housecarl, he needs a house before he is going to turn up and start guarding it.

If you are not thane, you get no housecarl, you would have to do the usual quests to become thane.