looks a lot like what I was gonna build, 750 bucks for a drawing, wow.
I’ve admired this one for packing a lot into a very small square footage with everything looking pretty usable and functional as far as layout, and it’s fairly pleasant to look at from the exterior as well:
https://www.houseplans.com/plan/777-square-feet-2-bedroom-1-5-bathroom-0-garage-cottage-39316
If cost to build is the primary consideration, though, you’d want a simple rectangular foundation and a simple roofline with no added gables. A shed roof is cheapest and simplest, although it only lends itself to contemporary or very, very rustic.