Gym membership price varies. Maybe start there. If you're /homegym/ then starting with body weight exercises might be a good start. Dumbbells are fairly inexpensive. A dumbbell/barbell package with 50kg was going on sale locally, I only looked at it because it was cheaper than buying 2 plates. It depends. How strong are you now, do you want to get strong or get big? Big and strong? Do you have gym near you that's cheap?
If you can get a gym membership it will be cheapest for long term strength development, probably. Shop around for second hand bars, benches and racks if that's not an option.