There are many ways to cleanse a house/apartment of previous owners psychic energies.
My grandmother used to do her own blessing of the place by taking salt water, sprinkling it on the doors and saying a Catholic prayer.
As for me, I will sometimes get some nice smelling household cleanser and wash the doors. Doors are like foot mats at the front of the entryway, they accumulate lots of psychic junk and attach to the doors.
Now when I want to really do a thorough cleaning, I use Reiki. I will stand in the middle of the room and draw or imagine the symbols in front of me and placing my intent on cleansing the room of all psychic debris. Then using my hands to help me put more action and energy into the process, I push the symbols to the walls and with hands facing the wall, I imagine energy flooding out of them energizing the symbols and spreading to each corner of the wall. I repeat this with all walls, ceiling and floor. Then I put the Reiki symbols into a big energy ball and imagine the ball becoming super bright like a lightbulb lighting every corner of the room. Repeat in each room and where ever you feel a need to do this work. If you are not familiar with the symbols, just imagine energy pouring out of your hands instead. Also, do this before you move into the place as your energies might conceal the previous occupants energies.
I know it sound tedious, however, it's good at opening your psychic self up as well. You will feel more sensitive and energized afterwards from channeling so much energy.
This is also a great way of protecting your home of psychic leaks from neighbors. I will sometimes, while meditating, imagine powerful cleansing, protecting energy pouring into my crown chakra from the Universe. I fill my body with this energy, then see it burst out of my body to fill the whole apartment.
Go with your senses. After the cleansing, come back later, but with your senses heightened and slowly go through each room, as well as checking each closet and see if you can pick up anything unusual. If you do, then zap it with an extra dose of Reiki energy.
Sincerely,
Zookie