I was thinking in renting a flat, but if we are planning to have kids in the future I would really love to BUY one instead.
That will mean saving up for about 3 years at least to be able to pay the down payment.. and im so unhappy here lately (this also affect our relationship) and I dont know if i should wait those 3 years or just get the flat..
Is there a better way?
I think it's going to be a case of working out your options and going for the one that will suit you best.
In terms of your current situation and the affect it's having on your happiness in the UK and your relationship, perhaps it would be best to just rent a flat to start with. That way, you can have your own place, without having to live in a small house with other people, and you can get your life in order living as a couple on your own. Then you can sort things out from there, and look into buying a house in the future.
On the other hand though, it may also depend on how much renting a flat will set you back and how much you will realistically be able to save towards a house deposit if you are renting vs. how much you can save by continuing to live with your in-laws... and whether or not you feel it's worth living with them for a few more years just to save the money, or if it will be better for your wellbeing to have the freedom of living on your own, just the two of you, during that time.
I would like to know also how much is for the down payment (generalizing) for a flat or a small house in London or in the surrounding area (even in the outsides of London) so i get an idea of how much i need to save up
I have zero knowledge in houses and prices or anything at all.. so I really need some advice..
House prices in the UK are generally really high, especially compared to the US. In London, it would depend on the area and size of the property as to how much it would cost, but in general, London and the surrounding areas are much more expensive than most of the rest of the country.
Up in Lincoln, where I live, I've seen small terraced houses on the market for £100,000 to £120,000. In Bristol, where I grew up, the same size houses go for more like £200,000. In London, terraced houses average £500,000!
You want to be able to put down as big a deposit on a property as you can - and it depends on mortgage companies/banks as to the lowest deposit they will accept, and how by a mortgage they can give you.
I'm not an expert by any means, but I would say you'd want a deposit of at least 10% of the property value, if you can save that much.
I started saving for a house deposit in 2011, while renting at the same time. By June 2013, I had £5,000, which is basically nothing in terms of property deposits. I have since been working abroad with my company, earning overtime and overseas allowances, plus I have had no living expenses for 8 months, and by March 2014, I should hopefully have about £25,000 saved towards a house deposit.
I will be renting a property when I get back to the UK in March, and then will consider my options for buying. I am tempted to leave it a bit longer, keep saving, maybe do another overseas tour next year to save a few thousand more, and then buy a house in a year or two. I will most likely buy a house in Lincoln, even though I'm not planning to stay there long-term, because it's where I currently work and it's the only place I can afford to buy a house.
If it were me in your situation, knowing how long it can take to save enough to buy a property (if not for my overseas work, it would have taken me several more years to save enough), I would probably focus on getting out of your in-laws house and into your own place first, and then think about buying later on.