A more typical number among my SaaS buddies is about 18 months of sustained effort until you hit $10k in MRR, which typically is enough (after expenses) to keep a solo founder in the field indefinitely.
The fastest I've ever seen it done is about ~6 weeks for SaaS. Even shorter for infoproducts, although depending on the dynamics of the business that might be "launch one, get relatively flush with money, buy yourself enough time to launch a second one" until you figure out some not-too-obvious things about how to sell them repeatedly.
A consultant, naturally, can hit day job equivalent levels of revenue virtually immediately after hanging out their shingle (if they've got a client lined up). A fairly common pattern is "Inform day job of intention to quit; immediately go back to working for day job as 1099 during transitionary period; start building pipeline while delivering for Client #1."
Best of luck at this new role :)