Do you think a just break even cash flow and slight negative cash flow is worth to hold the house?

That isn't easy, but probably gets you where you want to go.LTR also possible, but you probably need to have 30-40% down in the better neighborhoods to break even or cash flow.

They will cover rent if the tenant breaks lease or doesn't pay, however they won't pay the rent for in between tenants, so if they can't find someone for 2-3 months that's on you.

Putting less down may subsequently put you in a break-even scenario or possibly even a negative cash flow.

You'd be lucky if you break even on your mortgage payment at the end of the month (yes, you can end up owing them :)).

If the downstairs tenants are not yelling on the phone, purposefully slamming doors, playing loud music, etc. then it doesn't sound like they are breaking the rules.

It is all dependent on the numbers.If you are planning on putting low money down, the odds of it cash flowing (or even breaking even) in the first year would be difficult. 

These things hold their value amazingly well.If I had to guess, if you bought it for 40k and only used 9 or 10 times, the hours on the machine would be so low you could probably resell it for 35k or better (given that their retail value would go up over three years so the discount from say 48k to 40k might even mean you break even)..

I started out as a copywriter and I'm huge believer that you can make or break a sale based on copy alone.

The feds throwing money or tax breaks at housing wont solve the problem . ( It never has )  .