How To Start A Business

I’m looking to start a cleaning business for realtors or new construction or anyone moving or just moved into there home who needs deep cleaning done. Has anyone out there ever done this or doing this? Please give me advise how to start.
Thanks

I live in New York state, and am considering registering my business (internet - ad supported) as an LLC in Delaware. I don’t sell any products - I only provide online content. Would I need to register as a foreign LLC in New York? Am I considered to be “doing business” in New York if only my office is located here and all revenue is from internet ads?