Vacancy is not a surprise event; it is a normal property-investment risk that should be allowed for before purchase.
Budget for vacancy
Use a realistic number of vacant weeks in your annual model rather than assuming 52 weeks of rent every year.
Research tenant demand
Look at current listings, days to lease, vacancy data, new competing supply and the types of tenants the property is likely to attract.
Price to the market
Holding out for an extra $20 or $30 a week can be counterproductive if it creates a long vacancy. Compare the additional rent with the income lost during extra empty weeks.
Improve tenant appeal
Clean presentation, reliable heating/cooling, storage, security, functional appliances and responsive maintenance can all affect leasing outcomes.