What if the club doesn't have a team?

See if you can start one! This might not necessarily be down to you alone; with a bit of luck one of the other parents can be cajoled into helping or to take the lead role themselves.

What you can expect the club to do

Take care of all the 'admin'.
Supply playing kit and equipment (balls, first aid, linesmen's flags etc).
Provide a pitch with all the necessary equipment.
Give you their support and provide guidance on how the club is run, how the teams are run and helping you set up your own team.
Pay for you to attend a coaching course that also covers Child Protection and First Aid.
Pay for your CRB check.
Register your team in a league (if that is required) and pay all the necessary registration and playing fees.

What the club will expect you to do

Make a commitment to run the team the right way and in line with the way the club is organised.
Undertake a recognised coaching course. This is a 'must'. You will find it extremely helpful and it will give you more confidence; this qualification (with child protection and first aid equally important) is increasingly a minimum requirement for anyone that wants to be involved in mini/junior football. The course is often run over two weekends, but various associations will have their own coaching programmes that will differ in the waythey are structured.
Give as much time to running the team as it needs. Typically this could involve:

2 hours of your time per week in the evening organising a training session. One hour session with ½ hour either side to set up and then tidy up.
Saturday am or pm/Sunday am or pm for matches. The time involved will vary considerably dependent on the age group you're looking after.
Organising the team (and the other parents!). Team selection, making sure everybody knows where the game is being played, collecting the subs, getting all the match stats to the league etc.
Keeping in touch with the club. You might need to attend club committee meetings (monthly or, perhaps, quarterly).