When I bought my first house in my twenties I rented out my spare room to help with living costs. I advertised on Spareroom and soon found a lodger. She was tidy, quiet, respectful of my house rules, and always paid her rent on time so in many ways ideal. However, I almost immediately regretted it.
My lodger had moved to the UK alone for work due to a recession in her home country. Because English wasn't her first language she came across as very blunt and critical about things in the house she wanted changing. She was so homesick she spent most evenings crying. I tried my best to make her feel at home but she didn't want to engage so I retreated to my bedroom to avoid awkward encounters. It didn't feel like my home either, more like a houseshare.
Her initial contract was for six months and she hoped to renew it but by that point, my best friend had split up with her partner and needed somewhere to live. I was optimistic that living with someone I gelled with would work out better. Well... by the time said friend moved out 18 months later, we were no longer on speaking terms.
I was away one weekend and received a message from her to say her mate (who I didn't know) had come to stay for a bit because she'd had a breakdown and needed to get back on her feet. By the time I got home this random woman already had a key to my house which my friend had got cut without my permission. I told my friend I would have appreciated it if she'd at least asked, not assumed, and got back, "We always help each other out though!"
Days turned into weeks and this random houseguest made no effort to get to know me. She spent all day lounging around while my friend and I were at work, using my gas, electricity, and water, with no indication she was actively looking to find a place of her own. Because the rent I charged my friend included a fixed cost for bills I was out of pocket. After a month I raised this – My friend had the audacity to make out I was the unreasonable one because as a homeowner I was in "a position of privilege" whereas they were struggling in comparison. If my unwanted guest had offered to contribute I wouldn't necessarily have accepted but the assumption I would absorb the costs jarred.
I'd never argued with my friend before, but things exploded. The only plus side to this was that the random woman got the hint and moved on. My friend moved out too a few months later, having met a new man who had a place of his own. Things had deteriorated so much by that point that we didn't even say goodbye and I haven't seen or spoken to her in the ensuing 16 years, despite maintaining a close friendship with her sister.
I was done with lodgers, having tried the friend route and a more formal arrangement. Despite the financial stretch, I chose to live alone after that, which was blissful in comparison. Eventually, my now husband moved in and fortunately, that's one living arrangement that has worked out!
I don't wish to be overly negative and good luck if you do choose to go ahead with getting a lodger. I just wanted to share my experience of the pitfalls.