Sometimes you might want to go extra on something like the master bath or contemplate other exit strategies.

I can certainly tell you in SoCal if you had a single family home with an ADU that generates an extra $2k per month in income, end-user buyers will not be thinking "I'd pay an extra $20k for that." 

I'm extra cautious when analyzing a deal like this, but a lot of them end up being great.For interest-only financing, negotiating some principal paydown is a good idea.

I Enjoyed the extra viewpoint.

It may sound nice to pay a 5% management fee but the extra fees can add up to be more than the other company that charges 10% with no add-on fees.

I interpretttev @Alan Asriants statement different than you but agree it is not clear   He could be indicating pools, basements, sunrooms do not provide a means for an extra tenant.  

Many investors do end up getting their own license because of this, others don't want the liability and extra work.

You can't charge extra pet rent or even a pet deposit because it's legally not considered a pet.

One reason was the condo management company wasn't doing a great job and there were always extra levies. 

It's easy to obtain, costs very little, and doesn't require extra, on-going effort to maintain.