If you work at home, while those things would need to be done anyway, should be piped through your business to some extent since your business is taking advantage of those resources.

2.5x is the golden rule. You will need to double the salary to cover additional expenses (some of which weren't mentioned, like employer's side of FICA in the US, time spent on sales because contracts end, legal, etc.) you will incur. The .5 of that equation is your profit. Because you're running a business.