To keep your equipment in excellent shape, use a cover to protect machines and any foam padding from the elements. Consider using a light coat of oil or paint from time to time to keep your metal machines rust free.
You'll find a large range of equipment online on Gumtree. There's also a number of sporting goods and exercise equipment retailers that have bricks and mortar shops, although you'll need to factor in delivery costs and times for bulkier items.
This depends on your favourite kind of exercise and the muscle groups you'd like to train. The options are endless - from a spin bike to challenge your cardiovascular system, to dumbbells or a barbell to help build stronger muscles.
For a basic setup, grab a set of resistance bands for stretching and a kettlebell or dumbbells for body weight exercises. Consider a treadmill or exercise bike for aerobic fitness, or a multi station trainer for strength training.
Create a simple but effective setup using adjustable dumbbells and resistance bands for around $300. For $5,000 to $10,000+ you could build your dream home training studio, featuring commercial equipment like a multi station, a bench press and other machines.