I understand this is hard for you and changes in circumstances are impossible to predict, but I feel the need to be brutally honest here. Eight hours alone, 5 days a week, IMHO, is just not right for a 6 month old working cocker. If it were me, I would have to make arrangements for doggie day care or day kennels, regardless of cost, in the same way I'd have to make arrangements for childcare. I'm sorry to be harsh.
We have a worker and a show x worker, both aged 5, and we're lucky enough to be home all day with them (we're retired). I can tell you that they do NOT sleep, except maybe half an hour after their dinner at midday. Granted we don't spend all day training, walking or mentally stimulating them, but they're out in the garden puttering, or
watching interfering with what we're doing, or going in and out, or whatever, between their a.m. and p.m.
walks mad runs which take 2 hours or so.
We used to work full-time and we had 2 dogs but they weren't working cockers, they were aged 10 to 13, and they had each other for company. I think that was still too long and I felt guilty. I also found winters difficult because their morning and evening walks were in the dark and they could never get off leash except for weekends.
Sorry, I'm now off to hide
and really hope things work out well for you and Cassie.