When the time comes to make offers, remember your are purchasing a business, not a piece of property and repeat the mantra: "there will always be another property".I am prepared to invest up to $150,000 CAD ($140K USD) into rental properties.I would like my investments to be as passive and hands-off as possible, and so I would definitely be hiring a property management companyIf this is the case, then perhaps a better fit for your objectives is lending.  

The new legislation, which applies only to residential contracts for deed involving a serial contract-for-deed seller and an unrepresented purchaser, will not affect most contracts for deed.A companion provision amending the existing contract-for-deed injunction statute, discussed later in this article, applies to all contracts for deed and purchase agreement cancellations.

An appraisal, or a HELOC, on her personal residence can not possibly affect her taxes.  

A Mortgagee can actually affect and guard against such things.  

It will affect your return.

I honestly would recommend doing house 2 if your can borrow the money cheaply and it would not affect your business plan.

Overall, if we could repeat the exact same process I would probably be game, but it's harder and harder to find a lot or house that would work due to competition.

WHEN and HOW you can recover, in accordance to the Vendee/Buyer's capacity to pay will affect your return.  

All of the details not included in the post will make a difference on all of this but that is the nuts and bolts (some repeated) pertaining to the OP question.

In a duplex if you have a unruly tenant playing loud music disturbing the peace it affects one other tenant.