Sounds like the best of both worlds, doesn't it? A happy home life, but getting some kinky stuff on the side, without having to pay for it. I had this a few years back, with a retired SP that I had befriended, but it was actually more hassle and bother than it was worth. When you're not paying for it, they have more control over their availability, they cancel all the time on short notice, and they don't put a lot of effort into the session. Of course, it all depends on who your friend is, but for me it was not a reliable source of fun and relief. YMMV.
As for risks to family and business, well I guess that depends on your friend and your situation. Will she start wanting more than just a FWB situation? Would she want to hang out outside of her place (i.e. dinner out in public), which greatly increases the risk of being found out? The exchange of funds that takes place between an SP and client puts it on a more professional level, and IMO, brings a greater expectation of discretion.