PDA
You will need to keep accounts which the DWP will probably audit on a regular basis, items purchased for the business would come under expenses which I would expect would be offset against your income.
There are two types of Permitted Work (PW) both of which have restrictions that you need to be aware of.
The PW Lower Earnings limit allows you work any number of hours but not earn more than £20 per week.
The PW Higher Earnings limit allows you to earn up to £104 per week, but restricts your working to 16 hours per week.
Exceeding these limits will mean that you will be considered as being remunerative work and your ESA claim will be closed so be careful to manage both your hours of work and earnings.
Gordon
Nothing on this board constitutes legal advice - always consult a professional about specific problems 
