I am a (responsible & caring) landlord. I have long term happy & decent tenants:
There are a lot of legal requirements attached to being a landlord. Most cost money for certification etc. If you don’t abide by the legals then quite rightly your tenants can sue you if push comes to crunch. It could cost you a lot of money & stress. It doesn’t matter if they’ve punched holes in the doors, soiled carpets with dog poo, used the place for drugs, if you don’t get your legal stuff right, the might take you to court with a counter claim. (See the Shelter charity web site.)
If you are buying leasehold the service charges can go up massively over the years over which you may have no control; building insurance, communal area cleaning, ground rent, grounds or garden upkeep etc.
If you are buying leasehold look into the costs of extending a lease. Look up the term “marriage value” in case you need to know about that too. As a lease ages, shortens, it becomes harder for your buyers to get a mortgage. Look into that in case you need to know in future.
Not all tenants are decent people however lovely they seem or good their references are. Some tenants will absolutely trash your place, stop paying rent and cost you thousands in legal fees. You will have hardly any recompense for this without a load of stress or hassle. In effect it’s criminal damage but you will be powerless when it comes down to getting any compensation.
You will do well to have a slush fund set aside for maintenance and upkeep. A new boiler can be £3k+. I have recently replaced the double glazing in my rental property. It cost nearly £7k. I have recently had to replace their free-standing cooker. All in from Currys it cost over £500. I have the gutters cleaned out annually (big trees’ leaves) that costs £80 a time. Boiler servicing was £90, a faulty shower was £150. A water pipe leak in the garden cost me £350 because the plumber had to fig before he could fix it. So you see it’s not all it’s cracked up to be and then there’s accountancy fees and HMRC.
Agency fees can be high. There are some good responsible agents but some are rubbish. There’s a lot of rubbish ones spoken about on various Landlord forums on Facebook. They take your fee and do eff all. I self manage because of this. I have a list of tradespeople I call on. Agencies will have lists too & charge you a mark up if their trades are called out.
Consider void periods. Can you afford the mortgage if you don’t have tenants for some weeks/couple months? Referencing takes time. There are prospective tenant time wasters who will let you down at last minute. Agents charge £++ admin fees throughout the process.
If you keep data on your phone or laptop or on paper about your tenants, even just their phone number, you have to register with the Information Commissioner's Office. There is an annual fee for this.
As you can tell, it’s not a money making machine. Do your due diligence. Look up the Gov.uk website for tenants and landlord rules & regs. Join a landlord support group like the NRLA and research research research. You could get stung really badly if you don’t keep up with legislation.
CAVEAT EMPTOR! Good luck.