The alternative is a mound system, which you can expect will run 6 figures to install.I have heard stories of parks that make very little money, if any, because the pump truck expenses eats all the profit. 

But looking back, if a 1 child family tells me they are expecting again, I wince a little as I say 'congrats!' 

For turnkey I expect around 8-10 percent, personally.

In the case where a property owner is using a management company to manage their property and someone get's hurt due to negligence, i.e. management company does not fix broken stair and tenant falls on stairs, or a tenant complains to the management company about a mold problem, but the company does nothing about it, and the tenent gets sick, who is liable, the management company or the owner of the property, or is it both.

Now I'm expected to do 5-10 this year alone.

The one thing that I've found is that most markets are unique in the expectations the students have.

I am wondering what the average investor can typically expect for a return when they do their homework.

You should not be expected to go under contract before at least knowing the financials. 

looks like you no longer have this issue.But in the future if it happens again what's been mentioned so far - screen the new tenant, fill out application form, collect app fee, and have all existing tenant sign.IN ADDITION, make sure the existing tenants and new tenant understand, and include into the addendum if necessary, that all claims, damages and deposits are shared by all tenants from this day forward.That means if you see a broken window and need to charge them for repairs tenant C can't say oh it's broken before I moved in.Or if tenant B moves out and six months later you charge a deduction in the security deposit on a hole in the wall behind the couch he says the hole wasn't there when he moved out so it's not coming out of his deposit.At the end of the lease when you refund the deposit it will be a check to "A B and C" jointly regardless of who might be there or not at the end of the lease. 

I know of one agent who is expecting quite a few multi-families to be coming on the market in the Temple area shortly.