Ok, I got a couple ideas I want to put on T-shirts. These designs I want to put on t-shirts have designs with 1-10 colors and semi-detailed. Would I need to go heat transfer, vinyl system, or screen printing to go the cheapest route?
well it depends but here is what i think
the one color screen print setup has a high learning curve u will
need an exposure unit range from 20 to thousands
screens average 20 bucks
emulsion and fabric paint and squeegee not that expensive
for more colors
well heat press from the high 200s to more
low learning curve and specialty papers is pretty affordable at around 35 cent a sheet depending on how you want your designs to look. hope that helps
Could I print my images on the right paper and transfer it on there with heat from a iron?
An iron won't get hot enough and won't provide even heat. You'll probably be able to get the transfer to to apply but it won't last more than a few washes. Most transfers need an even heat of around 350 degrees or more, depending on the transfer.
Ok, I got a couple ideas I want to put on T-shirts. These designs I want to put on t-shirts have designs with 1-10 colors and semi-detailed. Would I need to go heat transfer, vinyl system, or screen printing to go the cheapest route?
I think the cheapest setup would be to not print the t-shirts yourself.
Leave that to company's that are already setup to print and just focus on the designs and marketing.
If you already have the designs, you can get them printed only when someone actually buys one by using one of the Print on Demand (POD) fulfillment services like CafePress, Zazzle, PrintFection, Spreadshirt, etc. They can print with Direct to Garment printers that can handle 1 color prints to designs with hundreds of colors.
You don't have to do it all yourself Sometimes the best option is outsourcing until you have made enough money to take on more of the tasks you have time for.
What is the cheapest setup to start out 
Sometimes the best option is outsourcing until you have made enough money to take on more of the tasks you have time for.
