SSO has various levels. You can do a "Login/Signup with Google" using any of the popular frameworks in a day or so. On the other hand, if you need to do full Enterprise level SSO (SAML, Audits, SCIM etc etc), you have more work to do.
Look at it this way. If your product solves a real problem for your potential customer, they wouldn't care about how to signup for it. Not until they tell you that SSO is a must. Until then, don't sweat it and keep going.