Model's stand

[Tito Champena]

I'm a beginner painter who wants to become a portrait artist. I have finally finished setting up my own studio at my house, luckily with a North side window. My new task now is to obtain a wooden stand for my sitters, because I understand that I should try to line up the model's eyes with my line of vision. What should be the dimensions of the stand? Can a stand be made ajustable to various heights? Do I have to hire a carpenter to build it? I will apprciate your advice.