What is the best exercise machine to buy ?

I agree the road outside your home. It is free. Start walking or running. PS I bought a Sole Treadmill and have gotten my money's worth already. I use it at least 3x's week. I mix up my workouts running, treadmill or DVD's.

Hope this helped. Enjoy.

Power rack, good Olympic barbell, weight plates all bought online cheap.

This depends on if you have the space.

I guess people dont read. OP cant go outside because they have to answer phones for work. So everything has to be done inside. Also OP has arthritis which limits their movements.
I have a treadmill and an elliptical. I love my treadmill but the elliptical is low impact and doesnt hurt my joints as much. I bought the elliptical when I injured myself and couldnt use my treadmill for months while I healed. Now I am back to my treadmill.

You enjoyed your treadmill obviously, so why not get a new one? Otherwise I would say elliptical. Or look into something else thats low impact that you would actually use. I would say this though, don't buy something new unless you actually love it and are going to use it. Go to a sporting goods store just to try something else out. If you like it then go online to find the best price. If you dont find anything you like then stick with the treadmill. Go to Treadmilldoctor.com they do all the comparisons for you and tell you the best models for your price range.

If you can afford it, a stepmill. My favorite all-around piece of cardio equipment.

Otherwise, a treadmill is great for manipulating conditions you may just be guessing about on the road: speed, incline, etc.

Also, I'm a huge fan the switch plate adjustable dumbbells because they take up far less room than a full weight rack. I have a pair that Gold's makes that are awesome. Weider makes some as well. There's a ton of resources online to create your own circuit (bodybuilding.com's "workouts" link has plenty of programs and exercise tutorials that require no gym). Don't neglect resistance training! Your metabolism will thank you

Nike lunarglide +5 (running shoes)

I guess this won't work if you can't leave your house. sorry. I take back my recommendation.

Gym membership! Unless you have thousands of pounds to spend on equipment, the cheap stuff is just not worth it.

They said they can't leave the house due to having to answer phones for work

TRX or similar suspension training. Great for body weight training, nearly infinite exercise options, and doesn't take up much room.

IMO