A few words of encouragement and caution:
1) Many casters have come and go. I have a theory that this is for two reasons: their product is not high quality or they don't run it as a real business.
2) Many casters that run it as a business lose their passion for their now-lost hobby. I have been close twice. In these instances, it pays to step back, stop trying to do EVERY car imaginable, and to focus on quality and stuff you love. I've had lots of folks ask me to cast a Yugo - I don't want the car, so my interest is ZERO. It is hard to work on something for months sometimes if you don't love it.
3) Many casters become overwhelmed - get an order from a customer and try to get it out next day. That is one sure way to make yourself fail. I have the following information on my webpage: "IMPORTANT! PLEASE NOTE: Depending on the number or orders I receive in any given week, it can take up to 2 weeks for me to make your kit. Additionally, I only ship orders on Friday or Saturday morning as I live in a rural area and work a real job! Thanks for your understanding!" I get 95% of my orders out in just less than one week, but that is as good as it will ever get. *** Remember, this is NOT your main source of income, your family, or anything else of importance. It is a hobby/business. It is secondary to the wife, kids, house chores, Scouts,Church, and anything else you are into. Missing a kid's ball-game, dance recital, etc. is the easy way for a spouse to HATE your slot cars very quickly!
4) Paraphrasing Lib: "Cleanliness is important!" It's not just part of the Scout Law, but paramount to good castings. That means keeping the shop surfaces, the molds, and anything tied to the master clean. Here's my shop most days:

Mind you, the surface is no longer that pretty, but I keep it scraped clean of resin residue and vacuum the entire shop every time I'm out there. Your wife will thank you for not dragging in little pieces of resin all over the house too. I also keep my molds in a cabinet that keeps them in a cool, dark area. I get excellent mold life, and I never pour more than 2-3 bodies of one mold in a 18 hour period. That's my rule and I get repeated 50-100 pulls per mold.
5) Back to #1: Many casters come and go because they don't run it as a business. The supplies are NOT cheap as Libby mentioned. I use high quality products and pay $500 for a 5 Gallon bucket of silicone and $100 for a 1 gallon kit (2 - 1 gallon jugs of P1 and P2). Mold release is a must in my book as well. I highly recommend getting either Quicken or if you love spreadsheets like me, track all of your costs, sales, etc. Not only do I claim taxes, but it ensures I have money in the account to pay for shipping, supplies, etc. I just shipped a 30 car order to Germany. Of the $1100 from the order, I paid $86 for insured & tracked shipping, and $30 for shipping supplies like labels for each box (they go on a shelf since it is a hobby shop), new boxes for each kit (I do that for ALL my orders) and packing peanuts, tape, tissue paper, etc.
6) Lastly; QUALITY. If you want to last, make a good product. You will still sell a few of anything no one else makes, but if you focus on making a massive selection but can't deliver on a product that is reasonable to make and looks decent - don't bother. I have had more complaints about other caster's products than I care to remember. I have a "wall of shame" I've kept to showcase these. Good night, Nurse! I should take some pictures, your toes would curl. I know of only one of those casters that is still around, and the only reason he is still in business is that the country he lives in is too far for most of us to go to kick his backside for selling complete garbage.
I didn't mean for this to come across as preachy, I have just done it for 10 years now and am still around to tell the tales. When Libby started, I was excited to see more 1/43 starting since I didn't have the time to do it and had been begged for several years from the folks in 1:43 to cater to their scale. Likewise, I'm excited to see what you folks in 1/43 have got going on and think it is a valuable service you offer to this scale. Looking at some of the work you all do is awesome and I don't know many as crazy as Bill that paint things so freaking fast. I think I complete 1 car for each 150 of his LOL, and his paint jobs are still better than mine!
Good luck, can't wait to see this take off for you!