Stefan,
I would classify this as a hybrid because the owner is also carrying back their equity in the property, not a straight subto; regardless, there are a few things you need to protect yourself in the deal.
First and foremost I would suggest putting this property into your LLC, or even a new trust named after the previous owner, but listing you or your holding company as the controlling member.
Included would also be a Limited Power of Attorney to give you rights to update/modify/change/payoff, and discuss all things pertaining to the mortgage and the existing insurance polity. You will need this to modify the insurance to list yourself as the sole beneficiary to the insurance in the event of a claim, but the previous owner will be listed as an additional insured to satisfy the mortgage requirements. Otherwise the insurance will pay to the previous owner in the event of a claim.
You will need a change of address request signed by the seller to the mortgage company to send billing information to your address.
You will need authorization to release information pertaining to the insurance or mortgage to you/your LLC.
You will also need to transfer all Utilities to your name (using the same above documentation).
You will also need to get access to the login info for the mortgage. Its best to just use the current mortgage holders login information, and not change anything. Move the payments to your bank account and setup auto-bill-pay or setup a mortgage servicing company to do this for you.
Obviously you must transfer the title into your name. This can be a challenge in itself as you need to find a title company/closing attorney that has experience in subject-to transactions. Most are not experienced and can put you in a really bad spot if you try and use one that hasn't done this type of transaction before.
DM me if you want to jump on a call and discuss this in further detail. I can connect you with a great company that I use to help with all the paperwork, contracts, and finding a good title company/attorney.
As far as the deal goes, I'm not sure what insurance, management fees, repairs and vacancy pencil out at, but these could kill the cash flow. A quick run of the number with standard assumptions shows that it could cashflow just over $1000 in year one. If you self manage, it could be another $3K in your own pocket. Depending on Taxes it could be a lot more.
Alternatively if you have 200K sitting around, you could possibly get better returns in another property, or possibly doing PML/PMP.