The cheapest home repair is the one you prevent. None of this requires special skill — just a calendar reminder and a few minutes each season. When a job is past your comfort level, that's the moment to call a trusted pro rather than wait for it to get worse.
Spring
Clean gutters and downspouts, check the roof for winter damage, test exterior faucets and sprinklers, and look over caulk and paint on south- and west-facing walls, which take the most sun.
Summer
Service the AC and replace filters, reseal decks and fences while it's dry, and touch up exterior paint while temperatures are in the ideal range for curing.
Fall
Clean gutters again after the leaves drop, have the furnace serviced before the first cold snap, disconnect and drain exterior hoses, and seal gaps where pests look for a way in.
Winter
Keep an eye out for ice dams on the roof, test smoke and carbon-monoxide detectors, and know where your main water shutoff is before you ever need it in a hurry.