、。
Common people's livelihood was making rice.
Literal
Common-people [attributive-の] livelihood [topic-は], rice [object-を] make [nominalizer-こと] was-[copula-past-だった].
A historical statement about pre-modern Japan. 庶民 ('common people, commoners') is the standard term for ordinary folk (as opposed to nobility, samurai, etc.). なりわい (written here in hiragana but usually 生業) is a literary/classical noun for 'livelihood, occupation' — old-fashioned compared to 職業 or 仕事. 米をつくること uses こと to nominalize the verb phrase.