What brick and mortar businesses with sub 5m start up generate the highest ROIC?

What brick & mortar businesses with sub $5m start up costs generate the highest cash ROIC? Please ignore businesses which require very deep domain specific knowledge that cannot be subcontracted through managers and employees. I’m interested in starting a business that isn’t strictly software. I’m also not looking for infinitely scalesble growth, VC funding, or the generally pervasive growth af all costs mindset. I’m looking for strong cash returns on capital with a fairly non technical business. I am willing to learn technical skills to a reasonable extent, but I’m obviously not going to be a good candidate for starting a law firm. I’m not a lawyer.

Expertise: I can program competently in data heAvy, math heavy work, I work in commodities trading, I worked as a quant for a few years , I’ve worked in business development, and in commodities trading risk.

Any ideas? Ideas don’t have to be remotely related to my experience if they can be learned by an intelligent person without significant years of schooling or credentials.