I am not a lawyer, but I can offer some general information. Taking someone else's property without their permission, even if it appears to be abandoned or discarded, may be considered theft or illegal depending on the jurisdiction you are in. It's important to understand the laws and regulations specific to your location.
In many cases, when an item is left on someone else's property, such as an apartment complex, it may be considered the property of the owner or management of that complex. Taking the bike without permission could be seen as theft or trespassing.
If you're interested in the bike and believe it has been abandoned, it's recommended to follow the appropriate procedures to determine its legal status. Contact the management or landlord of the apartment complex and inquire about the bike. They may have information about its ownership or intentions for the bike.
If the bike is genuinely abandoned and the owner cannot be identified or located, it may be possible to work out an agreement with the property owner or management to acquire the bike. However, it's important to ensure you have explicit permission to take the bike and repair it.
To be certain about the legality of taking the bike, I advise consulting with a legal professional or researching the specific laws and regulations in your jurisdiction. They will be able to provide you with accurate and relevant advice based on the local laws that apply to your situation.