I have bought and sold many treadmills.
The best you can do is to get a used commercial one off craigslist.
I have bought 3-4 thousand dollar treadmills for 1-3 hundred dollars.
I would buy a Landice if you can find one.(not the 8700-just a little too old but a fine treadmill). Landice has a 400lb user rating and they are built to last.
Lifefitness would be my second choice.Stay away from all the bells and whistles those are the things that break and cost money to maintain.
Where in Cali are you? I will find one close to you that would be a good deal from CL if you want.Just let me know what area CL to look at.
Some Sole treads are good too.
By all means stay away from proform or any other dept store brand.Getting replacement parts for these is the problem.
Also stay away from the folding ones.they are conveinant but break alot more.
Here is a fitness equip forum I am on alot if you have any questions about specific treadmill or other equip.
Do some searching before posting or you might get flamed a little.They are harmless though.