Increasing your occupancy rate should not be an expensive task. Most companies try to use SEO freelance consultants in an attempt to build up their search visibility, and while this works to some extent, in today's competitive digital marketing sector within the travel industry, it is unlikely that you are going to overtake the likes of Airbnb or Agoda in the search-engine rankings.
Of course, local SEO is going to work to some extent because your hotel, property management business, or your holiday home website has every chance of showing up on Google maps if your SEO is correctly configured. You can even try Google Ads as a side option, but if you do try this latter route into gaining leads online, be very careful with the budget you set on your Ads campaign. You do not want to start to compete with big companies and end up paying a fortune when there is a slim chance of a booking being the end result of a click.