Talking to the LA and the information event is a good place to start.
When we went initially, we decided to wait until our children were a bit older. The main reason was the safer caring policies in that you care for a foster child very differently. For example, they would not be allowed in your bed, and I wasn't ready to stop my children coming in for a cuddle in the morning. I didn't think they were old enough to understand why. And I couldn't leave another child stood at the door whilst mine came in (obviously!). As they've grown up and started having sleep-overs, they understand why things are different when other peoples children are in the house. They don't bring their mates into bed for a cuddle!
There is very little respite in our LA for younger children, it is seen as too disruptive and causes problems with attachment. I've known carer's who have been desperate for a break, being refused. It might be worth considering older children, but it would depend on how experienced you are with that age group.
Emergency care goes to the more experienced carers as it can obviously be quite traumatic (thinking the middle of the night removals). Otherwise they come in for short-term which could be up to 2 years +.
You are expected to do an awful lot in terms of meetings, contact, training, form filling. Our decision was that we could do this when our kids were in school, otherwise it would impact on them being dragged around, or looking for someone to look after them. There is a lot of work on top of just looking after another child, some of which would be hard to manage without finding care for other kids. For example, the standard contact with birth families for under 5's, is at least 3 times a week. That means taking them to a contact centre, picking them up and dealing with the problems and distress it often causes.
In my opinion, there has also been an over-recruitment of foster carers for younger children, and carers are being left on-call almost, whilst waiting for a placement. This is hard to plan what you are doing, and you are not paid anything whilst you are waiting.
Get the information, you will know when the time is right for you as a family. Go into it with your eyes wide open. My experience is that SW's sell stuff that doesn't quite happen in reality. We waited until our children were all in school, as that was right for our family!
It is quite a long journey, but good luck with it! Feel free to PM me if I can help!