You should try to get a sense of what your customers are interested in prior to spending any money at all. It sounds like you are not doing a professional slot car racing business and will be dealing more with casual and infrequent users. Based on what I see at dedicated slot car shops and hobby stores the most popular slot cars for infrequent and casual users is 1:32 scale slot cars.
The only downside with 1:32 is the additional space that a 1:32 scale track takes up compared to HO (which is now closer to 1:64 scale). Putting a 1:32 scale track on a 4x8 foot table does not provide a lot of racing action. If you can go to 5x12 then the larger table would be much better suited for the larger scale. One thing to also consider is that 1:32 is also available in digital, which allows multiple cars to run on the same lane. This alleviates some of the space issues and allows 4 or 5 people to be racing at the same time on a 2 lane track. Starter sets are definitely available in the price range you mentioned. The 1:32 scale cars are more expensive than HO, but the level of detail is stunning.
You have fewer off the shelf choices in HO scale. Tyco as you remember it does not really exist anymore. Mattel bought Tyco about a decade ago and tried to sell slot cars as childrens toys and eventually lost touch with the serious slot car enthusiast. Mattel does not take slot cars seriously and it shows. The Tyco/Mattel track is somewhat widely available as cheap yard sale and Craig's List fodder. The Aurora AFX line has fared much better. The AFX line was eventually acquired by Tomy and is now handled exclusively by Racemasters in North America. Racemasters is completely in touch with the serious slot car enthusiast and collector. The quality, variety, and support of HO products from Racemasters is second to none, approaching 1:32 scale in detail. The downside with AFX is the somewhat limited availability, you won't see it being sold at Walmart or most toy stores. Mattel's stuff on the other hand is toyish looking at best and support is pretty nonexistent. You will see Mattel in toy stores occasionally, providing raw material for future yard sales.
One potential compromise is 1:43 scale, slightly bigger and cheaper than HO and smaller and cheaper than 1:32. There are even digital 1:43 sets. This scale is just starting to gain momentum among serious slot car enthusiasts and it's hard to tell where it will end up relative to the other scales. If I had to assess the current popularity levels in slot cars I would say 1:32 is number one, followed by HO, 1:24, and 1:43.
Do some more online research and try to test the waters in your area to see what would generate the highest level of interest. Also try to look around your area to see what is being sold in the local hobby and toy stores. It would be nicer if your customers had easy access to the type of cars you are using at your place.
Keep it simple and focused on family oriented and casual fun. Good luck with your business endeavor!
