I can share my experiences on the financing side of investing, along with some of the experiences of my clients that are developers.

Quote from @David Contreras: How difficult is dividing land that used to be separate, but is now a large lot as a result of a voluntary merger by the previous owner ? 

Those that respond “$0” or something ridiculous, you can request income documentation from them to justify.Don’t be afraid to share with them how much your property taxes & Insurance increased and that YOU cannot afford to absorb them.ALWAYS get an increase or something of value annually when rents are increasing or tenants will start thinking they should never have an increase, making future increases that much more difficult to negotiate.

Assuming adding a vent isn't unduly difficult, i.e. the dryer being in an interior room far from an exterior wall and/or no good access to run dryer pipe, I would put it in on my own.

Some of our bookkeeping clients use it.

The click on / locking type seems like what most investors use, but repairs seem difficult without having to re-do a large area. 

If you were to seek a LOC against #3, you would not get much as an investment property its very difficult to get a LOC and they typically will not go above 75-80% LTV which is where you are at.2.

I almost always recomend my clients to install in unit laundry.

this is exceptionally difficult to do. 

RE is a get rich slow game and there are increasing number of people talking about how difficult it is to retire from your day job even with large numbers of rentals because cash flow is thin.On the one hand there is the Small But Mighty portfolio mentality which I believe is a book in the BP store by Chad Carson.