This is my daily schedule for a one man business (+ part time accountant and listing service) doing around $250K annually (split between 5 markets) with around $150k-160k being profit (95% thrift store / yard sale margins). This exact schedule is M-F, but I also work weekends on a lighter and more relaxed pace.
The obvious question is going to be about the amount of hours and whether or not it's sustainable. The answer to that is an emphatic no. I chose to put off hiring an employee in favor of implementing a listing service and grinding it out by myself for a bit longer, but will need to hire someone within the next few months to get some balance back into my life. My plan is to bring someone in to list (will continue using listing service) and ship, so it will free me up to focus more on sourcing and adding additional wholesale and RA stock to my inventory to diversify a bit more. As it stands right now, I'm relying heavily on technology, a tight routine, data-driven sourcing, and optimized processes to hold this all together. At a certain point though, I would definitely plateau or go insane without bringing in another body.
This is the tricky part about scaling up when manually sourcing one-off items and not specializing. You can make a really good profit percentage on your revenue, but it's definitely a grind and you have to be be willing to put in the work. This is the shit that social media influencers that sell everything under the sun aren't telling you. I personally love this path, but it's definitely not for everyone.