[mtmail]

I agree the title co-founder is obsolete after a year and proven business model. Clearly the new person starts with less risk, less equity a couple of less major decisions to make. Consider the title only if you know somebody you absolutely trust or can promote e.g. your first employee to that role.

Investors are probably looking for to minimize risk in case you become a liability. Bus factor (death, coma) is extreme but how about severe lack of motivation, way too much tasks for one person (un-doable) or burn out? On the other hand they simply might (secretly) object to the number of shares you'll hold and try to spread that to more people, e.g. to get you below 50%.