Majority of real estate wealth is built by increasing value, thus best to buy "below value" to have a better chance at increasing the property's worth--
1. Forced (doing rehab, getting better tenants, running better operations)
2. Passively (market getting better, rents increasing, buyer demand increasing)
Specifically, to Force Appreciation you usually look for:
1. Risk -- if there are problems to fix that others can't or won't tackle -- (mold, foundation, roof, HVAC, maintenance issues)
2. Market inefficiency -- if the property can be upgraded to better finishes/layout and the rent increases outsize the rehab costs; counters, floors, appliances, paint -- think kitchen and bath especially
You can also "buy below value" with seller distress-- that comes from:
1. Financial distress (divorce, death, other hardships)
2. Change in outlook (wanting to get rid of properties and move into other assets, or different phase of life)