Septic systems are generally quite trouble free. There are many, many vacation houses used only sporadically around with septic systems, and the owners don't do anything special to keep them operational. Poop itself has plenty of bacteria etc. to get and keep the septic action working.
Do check and verify carefully the legal requirements for your area. At least around here, installing a septic system is a rather expensive bureaucratic process with a good bit of regulation. The design needs to be done by (or at least stamped by) a properly certified Engineer, based on perk tests etc. made at the site, and various permits etc. obtained. It often runs in the five figure range before moving any dirt around. Commercial systems have yet more stringent requirements...I've heard of at least some cases where it's required to hire a state engineer/inspector to watch every part of the work involved in putting in the system. (It's always wonderful to have to hire someone to literally just sit around and watch the people you've hired to do the work actually do the work.)