Should I tear down my house and put in a modular?

1940s 3 bdrm/1 bath flat top on slab in Martinez (not annexed, county ordinances apply), California. It's paid for (no mortgage). The foundation is broken in at least 2 places. Neighborhood is improving, but has a long way to go. Other property owners have torn down and rebuilt, in some cases over-improving for the neighborhood. I am worried that access for delivery will be a problem as the streets are narrow. In order to sell and move, do I fix the foundation or tear down, and if I tear down, do I rebuild from stick or go modular? TIA