As you are probably aware - there are so many women who become mothers & give up work and think "I'll set up an online store so I can work from home"... and then there is an influx of baby/maternity/gift type websites that are all competing against one another. Some work... but I imagine that a lot of them struggle. But then - you say you want to target "working mothers" - so I'm still not sure what you are offering... a product, a service ? Would you have a website that generates income from advertisers (very difficult) or sell a product (costs involved in buying the products before they are sold & marketing). or sell your own services (which is your time that you are selling)...

If selling products you have to pay for all the stock on hand - and you also have to think of the marketing - and the cost of marketing.

I guess the biggest expenses for an online store are buying the stock in advance - and the marketing and the cost of setting up and maintaining an online store. You have to pay the marketing - even if you don't sell any stock. You have to buy the stock - even if you don't sell it. You would also have to set up payment options. You could do 'paypal'... but a lot of people don't like using paypal (me included). I prefer to pay direct with credit card. To be a credit card merchant, you have to pay a monthly fee, and a % on each transaction to the bank. I wouldn't bother with Amex or Diners... too expensive.

I sell skincare products online. I have had the website for over 10 years... and selling stock for over 5 years. There are very few people in Australia that sell my products online... so not much competition. 99% of my customers come from interstate. For me, the online sales are a side-line to my salon business. It doesn't generate a huge income yet. But I am hoping to sell the salon soon - and put more focus and marketing on the web sales.

Luckily I don't have to import the products - as that would come with another huge batch of expenses. So if you are planning to import any sort of product - then be aware of the huge costs involved in importing items.

Take a look at this link: Starting up online business? Help! - BellyBelly Forums ~ Pregnancy, Birth & Baby where someone else was planning an online store.

Depending on the items you are selling - you may have to consider insurance.
You would have to consider the cost of setting up and running an online website. That alone can run into thousands of dollars each year.

Definately do a business plan... and be realistic about the costs you will incur - and the amount of hours you would have to put into it. Do research into the other similar stores/sites. Find out costs of setting up a website... and how much it would cost to host it every year... and if you have someone else design it - then you have to pay them to make changes (add products etc).

The idea of setting up a home based business can be exciting...
But realistically - it can be very expensive... very time consuming... and generate very little income. It's best to think about the 'worst case' scenario - rather then dreaming about becoming millionaire mums. The current affair programmes often show the millionaire mums - but for 1 of them - I bet there are a 1000 that have gone broke trying. Unless you can think of something totally unique... But as soon as you think of something unique... someone will come along and copy it.

Good luck with whatever you plan to do. The government business websites are really helpful in setting up a business... and you can phone them and they are very helpful with advice & information.