There is an art to finding sites, you have to be creative. But before we look for any site, you need to know what strategy you are going to be involved in. This is key, trying to switch between a few of these will lead to frustration.
Land - Residential plots from 1 house upwards, infill, back/side garden plots
Commercial to Residential - Offices, low value industrial units, spare space above shops
HMOs & Buy to Lets (B2L) - Convert a normal house (C3) into rooms or find a high yield buy to let (C4)
Unbroken Blocks of Flats / Title Splits - A property that sits on one title but split into more than 1 unit