For self-occupied units (whether purchased or rented): It is advisable to choose 05, 10, 15, 20, 25, 30, 35...that is, floors ending in 5 or 0. Avoid choosing 03, 04, 08, 09, 13, 14, 18, 19, 23, 24, 28, 29, 33, 34, 38, 39...that is, floors ending in 3, 4, 8 or 9.
If the unit is only used for investment and rental: it is advisable to choose 01, 06, 11, 16, 21, 26, 31, 36...that is, floors ending in 1 or 6. Avoid choosing 02, 07, 12 , 17, 22, 27, 32, 37...that is, floors ending in 2 or 7.