Hey Cédric, totally can relate with you being from an expensive real estate market - I moved to Columbus a few years ago (from Portland, Oregon which was super expensive) to become a full time real estate investor, and ever since, I've completed quite a lot of BRRRRs, flips, and own a successful rental portfolio here in Columbus Ohio.

Option 1: Separate SchedulesCarryover: Continue depreciating the remaining cost basis from the relinquished property over its original depreciation schedule (e.g., 17.5 years remaining for residential property).New Schedule: Simultaneously, start a new depreciation schedule for the additional cost basis attributed to the replacement property, following standard timeframes (27.5 years for residential, 39 years for commercial).Option 2: Treat as New AssetCombined Basis: Treat the entire cost basis of the replacement property (carried-over basis + additional funds invested) as if it were a newly acquired asset.Single Schedule: Depreciate the total cost basis over the standard timeframe for the replacement property type (27.5 years for residential or 39 years for commercial).If you choose option #2, you need to file an additional form (4652) with your tax return. 

HI Jeremy, yes you would want to have a separate lease to each tenants if you are renting by the room.

The last 3 properties I bought were actually in almost move in ready condition.

Id like to take it out but if I do they would have to move as they now use it daily to access the upstairs. 

The method has many moving parts.

We plan on slowly bringing rents up until a tenant moves out and then we can get true market rent.

In my experience people that act like this generally are doing something shady with regards to how they are framing or selling the deal to the seller themselves and are trying to keep all parties in their separate silos. 

If this makes any difference, there is a possibility that we will move to a bigger home, in which case, the in-laws will move along with us, and we will either rent the existing home or sell it.

I believe that the easiest way to move forward is to buy a SFH and get a roommate or 2.