Don't worry about it. No car we've owned for the past 30 years has been garaged overnight, they are always parked on our drive. As long as the car is serviced & maintained properly, it will be fine.

Our 12-year-old car has spent its entire life outdoors without even the benefit of a carport. I can't find any evidence of its having suffered as a result. As long as it has no rainwater leaks around windows or doors you should be OK. Heavy rain will splash onto the brake discs and cause a bit of surface rust, but that comes off as soon as you drive.

Most people gave up putting cars in garages many years ago, but ours still shelters a 25-year-old car :-)

The battery and the brakes are the most to be concerned about.

Some cars are more susceptible to their brakes binding (sticking on) and/or the discs warping if not used for more than a week or so on a regular basis, especially if they are kept in a damp and cold environment. Using the car at least once a week with a reasonable amount of braking should be ok on that front.

Just make sure that you'd do a reasonable braking manouvre during each week's use - no emergency stop required (and not just after you set off either), but just avoid light dabbing of the brakes, in order for any surface rust to be removed and the mechanism to fully work.

As regards the battery (speaking for a standard car, not hybrids), again, a lack of use will inevitably drain the battery and likely shorten its life, worsened if that low usage is made up of short trips or in conditions that require significant usage of electrical systems, e.g. night driving and/or regularly in poor/extreme weather (headlights, heater or A/C, windscreen wipers, rear windscreen heater, etc) and the trip isn't long enough for the battery to completely recharge after the big starting drain and heavy usage during the trip.

A faulty alternator may make the situation far worse (poor charging of the battery when driving), though more of an issue on older cars over 5 years old. For ordinary cars in your price range, that should not be a problem for the most part.

I often have been faced with a similar issue to yours, e.g. commuting by train, and thus only using my car for the occasional work trip (most of them by train), visiting friends/family or leisure outing. As such, in the past, the batteries in both my cars I've owned since 1998 have gone through batteries every 4 years on average - especially when I've not needed to use the car for 3+ weeks on a regular basis. I have had similar issues on my current 14you Mazda3 on and off (when I've been using it sparingly) as regards brakes.

To mitigate both issues, using the car at least once a week as indicated should be fine, even during periods of very cold weather. I tend to now use my car once a week on a nice run when the weather drops below (at any time, day or night) 5degC for more than a day per week, once a fortnight when the temperature is between 6degC and about 10degC, and possibly (at most) three weeks when the temnperature is consistently above that.

As such, my current battery is still fine after 4.5 years, touch wood, and the car has less binding issues with the brakes. Cars do like to be used.

What I would do as well is possibly invest in either a decent, breathable car cover (if there's no chance in it getting nicked of damaged by local 'yoofs' for a 'larf') to protect the paintwork and lights from sun/rain damage, or at the very least park the car in such a way that the sun is not shining on the headlamps for long each day, as modern light clusters have plastic lenses which (unlike glass) deteriorate with age by 'frosting up', something which isn't cheap to fix it it gets bad and can result in an MOT failure.

It appears to have less of an effect on the coloured lenses for the brakes and indicators (unless they are clear and the bulbs are coloured).