I would suggest to buy another house.
As an electrician, I would love to see more people starting to build houses right now, as work is slow, but its not really smart if you are looking to save money right now.
I helped my dad build his house(3500sq ft. house, 2500sqft. shop on 2.5 acres) about 5 years ago and all the paperwork and permits and scheduling will drive you crazy. And I have been this business for 5 years and he has for 20+ years, even if you know what is going to happen and when, it is aggravating. My advice is if you do choose to build, hire a general contractor.
It is a good time to buy right now, prices are lower but like you said, it may be hard to sell.
I would suggest against a mobile home. It will be cheaper now, but if any repairs/upgrades need to be done, everything costs more. Most major things have to be bought from a mobile home store. There is no access to the attic and everything is sealed underneath.
Good luck with your decision.