I agree with all that has been said. I would steer clear of someone coming to your front door. I would also be very careful when dealing with local DME's as I had one charging me some questionable charges. When you go into the DME they will also sell you the CPAP machine that they make the most profit on. You have to be specific that you want a fully data capable machine and let them know which one you want. I purchased the top of the line machine from ResMed and I have no complaints with it. It keeps track of all sorts of important data that can help your wife and her doctor be sure that it is working for her. I have insurance but I decided to buy one online as the price was about the same as me going through insurance and I don't have to worry about compliance check's in order for insurance to pay for the machine. The best part about buying online you can purchase the machine you want, not the one the DME wants you to buy. It is your money and health so choose wisely. The dme doesn't have to live with the machine the next five years your wife does and she should be able to get the one that best suits her needs.
When I first spoke with my sleep doctor and looking things up online, it sounded like the DME would come to my home to set things up for the first time. After talking with my DME today, she said they don't do that anymore. Instead, patients come in and pick up the equipment and go through an orientation.
It is possible some DMEs still out to patients homes to help set things up, though I would expect them to call ahead and not just show up unannounced. Hopefully you got a card or something from the "salesman" so you can do your due diligence and follow up on where they came from and how they got your information.
I would check with your insurance and get the true story on what you deductible is, if you have a co-pay (my insurance only pays 80% after I meet my deductible) and if you need to rent the device for the first couple of months while you show compliance to therapy.
Even most DMEs are complete rip offs for what they bill you and your insurance vs what you get. Listen to the people here and take their experience to heart.
I just got a completely refurbished ResMed System One (550 model), which is an older model than what I had, but actually works like it is suppose to and sent my old one off for warranty repairs. Cost $429 total, and sent the invoice with a claim form to my insurance company this morning.