My fiancé came up with an idea he wants to start a cleaning service, I am behind him all the way. My question is how do we go about starting this? We are in niagara falls, ny area

Ok, this question is so huge that it really can't be totally answered in one or two postings. Hopefully many more of our friends here will add something.
I've started / run a number of companies over the years and have coached some startup people as well.
Three things are critical:
Do you have the necessary money to open and operate this venture?
Are you experienced enough to really be doing this?
Do you have the necessary money to open and operate this venture?

This is a starting point - there are a hundred more items.

The above answer is good. If you mean you are starting a cleaning service for homes and businesses, then following are some things that you might want to consider.

You probably don't need a license. But, I'm not sure about that. Definitely don't need one around where I live. You will need liability insurance. Some realty offices have gone into the insurance business. They are likely to have many carriers so you can then find the one that provides the best insurance for what you can afford. It may be a requirement where you live to be bonded. It is not where I live. I would speak with an insurance agent about that. Some potential customers might view you being bonded as being a plus. However, I find that your reputation usually precedes a person as well as how well he or she does the job to the satisfaction of the customer.

I am presuming that you already know what kind of supplies and equipment that you will need. Please don't forget about safety for yourself and others - masks, goggles, latex or vinyl gloves.

Advertising is important. If you do a Google search for Clough Quad Cities, then you will find ads for my various businesses dominating the first three or four pages in the search. Do a search for any of the things that I do and put in Quad Cities or any town or city nearby the Quad Cities, leave out my name, and you will still get the same result. All of these ads are free. If you take a look at how I have worded them, then you will get an idea how you could word yours. If advertising on the Internet is something in which you are interested.

I am listed in the Yellow Pages of the phone book for my two prime businesses. Also, I do occasionally list myself in a local newspaper. But, I still get more calls because of people who have my ads on the Internet.

Door-to-door is good also. Carry your business cards with you at all times and bring up what you do in casual conversation.

I would also suggest hanging an advertising "shingle" about your business wherever you can find a public bulletin board that you are allowed to post a business on - libraries, quickmart type places, bowling alleys, grocery stores, laundromats, etc.

Develop a reputation, and the word will spread.