It is the popular belief that building or buying your own house is simply, a cost. If you buy an old house you will have to spend an additional amount to renovate it and fashion it according to your wishes. Even if you do build a house according to your own wishes at the very beginning, after some time due to practical needs you might have to go for a renovation. However, your house doesn't have to be a cost only. It can also be an investment.
Renting out parts of the house
If you build a fairly larger place, more than what you require, you can definitely rent out some parts of it. It's not so difficult to call a handyman and get a partition going between your quarters and the rest of the area.
There are a lot of houses as such where the two parts are restricted to each floor when it is a two-story house or easily divided by a wall constructed later on. You can also use unused garages or rooms as short term rent out places. There are so many services and travel websites today that allow you to have home stays and the like. It could not only be a way to earn some money but also meet new people and have new experiences.

Use your garden
It no longer requires a large area of land to have a garden. You can easily have a roof garden, a hanging garden or a kitchen garden. There are a lot of new innovative ways in agriculture to grow smaller plants in tiny containers. You can also use bamboo like organic tree parts to grow stuff. You can hang them and save space.
If you do have a patch of land available, you can go for a small kitchen garden to grow some vegetables and herbs needed in the kitchen. This way you're not only saving money which you usually pay to the supermarket for veggies and stuff but also sourcing them from an organic garden. You will also have the self-satisfaction of growing your own food.

Consider Renovation
If you do not have extra space at the moment, still there are ways to add more space and make your house investment. Talk to a contractor and get ideas on how to increase space within a house. You can convert corners of the house to TV rooms, study areas, libraries and so on.
Extra space can be added to the kitchen by converting the space right outside the kitchen door. You can probably change balconies to living areas and convert the garage to a den or TV room. When you are converting garages like places ensure their security is not compromised, check garage door handles, alternative entrances and solid floor conditions.
Paint the place and hang some stuff; it will look brand new. You can choose an altered theme and decorate according to that, to differentiate the new part of the house from where you live.