WithMinimum.cs

public static class EnumerableExtensions
{
    public static T WithMinimum<T, TKey>(this IEnumerable<T> sequence, Func<T, TKey> criterion)
        where T: class
        where TKey : IComparable<TKey> =>
            sequence.Select(obj => Tuple.Create(obj, criterion(obJ)))
                .Aggregate((Tuple<T, Tkey>)null,
                    (best, cur) => best == null || cur.Item2.CompareTo(best.Item2) < 0 ? cur : best)
                .Item1;
}

Extension method to find the element in the sequence with the minimum value for a given property.

Usage:
private static IPainter FindCheapestPainter(double sqMeters, IEnumerable<IPainter> painters) { return painters .Where(painter => painter.IsAvailable) .WithMinimum(painter => painter.EstimateCompensation(sqMeters)); }