By not entering your location in your profile we've no idea where in the world you might be, nor what TV system you might be requiring!.
This obviously is rather crucial, there's no point building a TV receiver if it's not going to work in your country!.
By far the cheapest method is to use the receiver from an old VCR, these are often available for nothing! - most VCR's get scrapped for mechanical problems. For that matter, even a brand new VCR is likely to be cheaper than making your own receiver.