I'm a relative newbie as well, only been investing for a little over a year. My most difficult situation so far isn't a horror story, but a major annoyance, which could have (and may still) lead to an eviction:
I purchased a duplex earlier this year that was half rented. The tenants had been in the duplex since 2008 with no increases in rent...ever. The current market trends in my area are to have the tenants pay their own water bills; in addition, the tenants should have been paying almost 5% more for rent alone. This represents roughly a 20% increase in their rent since 2008. I'm in shale gas country, so rentals are expensive and rent quickly.
When I purchased the duplex, I gave the tenants a letter outlining the changes to the lease and included a copy of the new lease to be signed. The tenants initially refused to sign the lease, but were paying the new rate, excluding the water bills. I decided that I would continue to pay the water bills, but kept asking for money.
I was finally able to get one of the adults to sign the lease (there are 5 adults living in the house, gram, mom, son, 2x daughters). The adult that did sign only wanted a three month lease, so I acquiesced, but explained that they would be responsible for the water. Initially, they agreed. Five days later, the adult that signed, told me that she was "tired of paying bills, so wouldn't pay the water bill". I told them plainly "Well, water is not included in the lease."
When it came time for the lease to be renewed (only 3 months later), I hand delivered a 'nice' letter with the lease, again plainly stating that the water bill is the tenant's responsibility, and that simply not wanting to pay the water bill was not good enough to not pay; they owed for the back water bills. In the 'nice' letter, I asked that they suggest a payment schedule to pay back the bills.
Well, that letter got the tenants upset, and they brought me over to show me the 'cheap' cabinets that all had broken doors. The cabinets weren't cheap, the tenants simply live like...well, don't live like normal people; they had broken the doors. They also never suggested any payment terms.
I then drafted a 'stern' letter which dictated the repayment terms, laid out the costs for the cabinet repairs, indicated that only the adults listed on the lease were to live in the unit (all others would be removed) and said that if these terms were not met, the property was to be vacant by October 31. About one day later, I got a call requesting a meeting to discuss the payment terms and to give me the fully executed lease agreement (with all adults listed).
Through some additional negotiation (no new cabinets, but new cabinet doors), we came to an understanding. We will see what happens next month when the water bill comes.
While I should have addressed the issue months earlier, I'm proud of how the situation has so far resolved itself. I feel I'm on better terms with the tenants and that they are understanding the ramifications of the tenant/landlord relationship.