Some are and some aren't. Some are very reputable and are often the only alternative someone with a severely-distressed property -condition-wise - has to unload that property. These companies are usually of little help when it comes to properties facing foreclosure, unless there is a lot of equity in the property. If there is equity and the property is not in bad shape, it's usually better to put it on the market at a below-market price, which is still higher than what one of these companies will pay. They operate by being able to do the necessary repairs at cost, fixing these properties up for far less than the homeowner could.
I took advantage of such a company's services. I was about to become executor of my father's estate and had four properties to deal with. Three were marketable. The fourth was a disaster. If the town had gone in there, they would have condemned it and ordered it torn down, it was that bad. I called a 'we buy homes' broker, one I had never met but knew of while I was selling real estate myself. He had been buying homes for many, many years. We agreed on a figure, a very low one, with a fast closing date. The price was less than I was hoping, but it was more than what the empty lot was worth after the expense of demolishing the house and hauling away the debris. It was the best thing I could have done in the situation I was in.
That house needed, easily, if I had to hire it done, 70k in work, in an 80 - 90k neighborhood. It would have taken the better part of a year, and then I would still have had to sell it and pay commission, plus the taxes all that time, another few thousand at least. The seven thousand I took for it looked much and much better, and it was fast and easy.
I found out later on, when I called this same broker to help out a friend that needed a quick sale, that he lost money on the house. Said it was the worst outcome he'd ever had. A basement wall collapsed three different times, twice after repairs, due to drainage problems that even experts couldn't figure out how to fix. Also, it turned out that the house, in the oldest part of an old suburb, had never hooked up to the sewer system when the rest of the neighborhood had changed over forty years earlier. It was still on leach fields, not even a septic tank. Apparently the town didn't keep good records. My father was lucky all those years it was never caught. That alone cost this broker many thousands.
You've got foundation work and mold issues, both probably related to poor drainage. Cosmetics are easy, new roofs and doors and windows can easily add up to a nice chunk of change, but the water problems and the mold? Those are really serious. I think a fast sale is your best bet.
Just do your due diligence and investigate these outfits before you pick one. Talk to them first, get a feel for how they carry themselves. Ask each for references. The good ones are licensed real estate brokers. Find out if they belong to the local Board of Realtors and see if they are members in good standing, find out if they have a record of complaints.