Power Washing. After the winter with all of the salt and dirty snow, your rental property may need a good power wash. Many places will rent out a power washer for a day and they are relatively cheap to operate as well as rent. Obviously it is better if you have a friend who owns one, and the beauty of social media is that you can easily ask around. Check classified ads if you are interested in buying one, you never know what will pop up!
Planting. Getting your hands down into the dirt in the beginning of the spring can be a great feeling and extremely rewarding. You may want to plant a couple of flowers around the lawns or maybe a tree or two for shade. You may even want to create a memorial garden of some kind, either one that is for someone specific or one that others can use if you own an apartment complex. Perhaps you have been thinking about starting a communal vegetable garden. Ask around with your residents and see if there is any interest in keeping a couple of plants and herbs alive for the community to use.
Paving. This is always a big one after a rough winter if you have an apartment complex with a parking lot. Plows and snow wreak havoc on asphalt, and so you may be thinking about patching some of those pot holes left behind. While it is certainly expensive, it will be more than worth it in the long run for you and your residents as well as any guests they may have over.
These are only three things that you may want to consider doing now that the weather is warming up. Stay tuned for a couple more ideas if you want to keep improving your rental property.