Yes you can have him as a partner in the business.
You have 3 tax returns - yours, his & a joint
You can do this yourself, but will need some specialist software because its a partnership (£99 - £400 depending on what you go for)
I was in a partnership with my wife and we did it ourselves one year - my advice - get an accountant to do it ... is ALOT of hassle doing a partnership tax return yourself