An arm's length mortgage is one where the person you're giving the mortgage to is not related to you (ie, not you, your spouse, parents, kids, grandparents/kids, or a corp you own a signficant part of). They're safe in that you are typically on title so if the payments stop, you can foreclose and have a better chance of getting your money back. That said, if you're a second/third mortgage, the risk goes higher of there not being enough value in the property to pay everyone back, and you're second/third in line.
Additionally, I'm not sure that 10K is really enough for these types of situations. There are legal fees involved typically, and your RRSP provider will usually charge a decent fee to administer the mortgage on your behalf.
I have not actually ever done a RRSP mortgage, largely due to the part where I didn't think I had enough to work it properly. I know there are companies out there that offer to allow you to use your RRSP in small chunks (often 10-25K) and own property outside the RRSP while loaning the money inside. I worry about these as I'm not sure that General Anti Avoidance Rules wouldn't kick in, but I'm not sure that's what you're even looking at.