Hi, I think you haven't gotten responses because you've wrapped about a million questions into one! It would probably help if you focused on the most basic ones first. Budget and location come way before countertop materials (I know how tempting it is to jump to what I call the "fun stuff," though).

I like the houses in the links in your post, but I'd be surprised if you can get that for 150. SF anywhere near Boulder. As to whether or not you can ever sell a small house, of course you can-- you can sell anything if the price is tempting enough. But if you want to know if you'd get all your money back selling any custom home, that's another question!

I recommend you back up a few steps and ask Question 1, then question 2 and so on. Good luck to you and hang on to your enthusiasm!

Start with the first question:

Can we buy a lot?

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In and near Boulder, CO buildable land is scarce and expensive, and permits are hard to get. Because of sewer and water issues, there have been moratoriums on issuing permits in some areas.

First, find your lot.

Lots can be found in Erie, and Longmont has potential for complete tear downs. Boulder County is quite a bit larger than just Boulder City. We also haven't ruled out the surrounding areas, but we do both work in Boulder County right now.

50K is too small of a budget to even begin to think of such a project. As far as building for 150K, here in TN where the land and labor costs are less than half of what they are in CO, that would buy you a modest starter home. Very few upgrades. If you wanted the same square footage done in a specialty construction method, or you actually wanted a smaller home, the price would go up. There is a certain economy of scale and repetition and when you get outside that model, you pay extra for doing so.