What kind of income threshold …

A British partner of a person applying for a spousal visa needs to meet the minimum income threshold. They must earn a minimum amount of income equal to or over £18,600 per year for a visa application to be approved ^[1].

The minimum income thresholds must be met for 12 months. Applicants must provide evidence to show that they are able to support themselves and their partner without any government help ^[1].

References:

1. Income Threshold for Sponsors of UK Partners, gov.uk