+ Company secretarial + Property leases + Contract negotiation + Management accounts + Investor management + HR + Compliance + Risk management
These could all be taken care of by a single professional in the early days, and handed on to pros as things grow. This person would cost less than a single SV dev! Why would you want to try and learn all of this the hard way? Is it a control thing?
Many of those issues such as HR, Compliance, Risk Management, Office Space, Laptop Computers and WiFi are handled by other units of the larger organization. Unique contracts though are handled by the executive director or somebody close as I think should happen in any organization.
I have worked in many startups around that size (they'd call it a small platoon in the military) and past 20 persons you would normally need a full-time HR person and there would be CFO, COO as well as the CEO divide the other work. If you are lucky you are in a startup accelerator that gets you a swanky office. Your CEO might be out of the office more than half of the time doing investor management if the firm is doing a raise.
In a 4-5 person startup you might find one executive who handles all that but employee #4 was a secretary who does as much executive stuff that can't be done by the CEO as possible. You are very lean on office space, you WFH like Mark Benioff did back in the day and save on office space.
What are you proposing?