Wife owns a number of creches so I know something about this.
As mentioned above good staff are difficult to get. To get and keep good staff you will have to pay over the industry rate and may have to pay for them to do the basic qualifications. Many parents object to having non native english speakers looking after their children as they worry about the childs speech developement.
Staff children ratios mean that you will have to charge a minimum rate just to ensure that the x number of kids that a minder / teacher looks after pay her (it's usually a her) wages and other costs. In a larger creche you may need a 'floater' to move between rooms to allow other staff to take a break.
Insurance is not that expensive. Kidd insurances have a very good group scheme and you should be able to get good cover for less than €1k in most cases (€16m EL / €6m PL / Property / Cash / BI / etc).
Equipment can be very expensive, especially montessori equipment.
If you prepare food on premises then HACCP regulations apply and you must register with the HSE. If you buy in prepared precooked food then it can be very expensive.
Building maintenance costs are as per other buildings, e.g. fire alarm, fire extinguishers, etc.
If you are coverting premises then it can be very expensive as to get a fire cert you will have to install additional fire escapes and fire doors throughout. You may also have to subatantially modify your exisiting kitchen. Talk to the HSE before you do this as they may have objections to the way you have done something and it is best to hear this before you spend any money.
The Health Board will inspect once a year but if you keep a good creche they are no real problem. However they do sometimes come up with some weird and wounderful suggestions that are completely impractical but which then appear on your inspection report.
Finally some parents are a pain in the ar*e to deal with at times. After 10 years in the business the behaviour of some parents still continues to shock e.g. dropping of your child for a full day on the way home from the airport after a weeks holiday and an overnight flight! If you live in the creche premises it may seem like you will never get away from them.
As mck26 said, do your business plan. Despite belief to the contrary creches are not a money making machine. To make good money you need to own more than one or else be prepared to work in your creche full time as a staff member.
Finally don't depend on a state grant. We have been told by the Child Care Commiottee where we are based that the 2007 money is all gone; and the 2008 money is earmarked for aplications received before late 2007. If you apply for a grant now it will be 2009 before you have any chance of getting it.