I inherited a flat from a sibling who died, which I let out. At the moment I have some very good tenants, a retired couple who have told the agents they want to rent long term. They have been there for 18 months, they paid the first six months' rent in advance, and on renewal paid one year up front too. If they renew again, which I hope they do, inspite of management agent's advice on the last renewal ,I will not put up the rent as I value good tenants over an increased rent. As far as tenants go, I have had a mixed bag, including one of my sons for a short period, who paid mates' rates and shared it with a rather unreliable friend. Prior to that I had two flakey young girls who were consistently late with the rent, although paid it in the end. They also let condensation build up because they were somewhat inept. My first tenants were a couple of young doctors who were also good tenants, although one of them did manage to put the exact image of an iron via a burn mark in the smaller bedroom,clearly no ironing board although he admitted liablility and was happy to have the cost of that deducted from their deposit. It caused us much mirth at the time because his name was Dr Burns
My flat is fully managed by a letting agent, Their fee is 11% of the rental income plus VAT. The flat is way down in Surrey about 25 miles from where we live, if it were nearer then maybe we would manage it ourselves although of course that can be a hassle. The managemet company have a panel of workmen who they can send round asap if there are any domestic issues. It's their responsibilty to place invest the tenants' deposit. They make a retention out of the rent money against any necessary work that may occur during the tenancy. As the previous poster has mentioned each time a new tenant takes up residence there are a raft of reports required such as Legionnaire's, electricians, fire alarms and an independent inventory, which is quite important as it provides photographic evidence of the state of the property so when the inventory is compiled again at check out it should, but doesn't always negate any issues regarding damage, but not everyday wear and tear, carried out by tenants. All in all the setting up cost with the management company are considerable and can take a very large portion of the first month's rent. Even with an ongoing tenant they still charge a hefty sum to draw up a new renewal agreement each year. It's also wise to take out an insurance against tenants defaulting on rent, this covers the cost of legal fees to regain possession of the property and recover rent lost (a worst case scenario) The owner is also liable for the management/service charge which most blocks of purpose built flats, in my case that is paid twice yearly.
If the flat lies empty, I had a few months between tenants when we were redecorating and up dating, then after a few months grace, the owner is liable for the Council Tax too so you need to bear that in mind.
It's certainly something to consider with such low interest rates, although you have to build in costs you may not have taken into account op and of course no doubt you will have researched the area where you intend to buy as to the market and how quickly properties are snapped up for rent. However, I know that I derive an income from my property and if I were to sell that would come to an end and I would just be running down capital.