Can I deduct small business start up expenses, i.e. Subscriptions, computer, domain name etc. without having an LLC set up? Or do I need to have the LLC up? Tnx

An LLC is a legal form of business, not a tax one. As far as the IRS is concerned, you are either a sole proprietor, an S Corp, a C Corp, or a Partnership.

You deduct start-up expenses after you are actually in business. Not yet having a product/service to sell = not in business.

Thanks SJ.  Can I deduct expenses/costs incurred in 2017 in later tax filings say 2018 2019 once I do have a product to sell?

Yes, all expenses paid to set up a business will be "Start up Costs" when you open the business.  If the total Start up Costs are over $5000, the amount over $5000 would need to be spread out over 15 years.