Creating a unique ecommerce online venture will usually require about $10k, however the costs may still climb if you are looking for more functionalities like in a existing popular website. Developing a booking platform will require about $25k-$35k. Since you are going to make use of the Indian web developer or an agency, you might cut around half of the price. When you are looking for a booking platform, you might want to consider these things,
Go for intuitive features and dynamic forms
Most of the booking based websites make use of easily understandable forms and features in their websites. They try to make it quite simple for the users to book a specific thing. In order to find the right listings and getting the information from the users, you have to make use of the dynamic forms. Even the sites like Redbus or MakeMyTrip makes it easy for the customers to book things easily. You should not make it more difficult for the users the use the website. The navigation and the forms used in the site should be intuitive even for the common people.
Get the options to approve and manage the listings
When your clients are adding up a new listing in your website, it should not go without the manual moderation. There might be chances for posting up of irrelevant listings in your site. For this, you should have the options to approve and manage the listings. Request to mail you an alert whenever a request is made for adding a listing. You should also have the options to edit or modify all the content and images in any listing.
Maintain an effective revenue and business model
Earlier I had an opportunity to use a rental website RentSher, it is one of the best Indian rental site i have used. They make use of the effective business model. You should set the fee for posting a listing, advertisement banner, advertisement captcha and membership. There are also options to earn revenue through the payment gateways and other options.
Ask for launch modes and extensive insight for the site
When the website is going to be launched soon or under any repair for server error or any other issue, there should be launch modes to display a message about the status of the website. Usually you can see the pre launch modes set for the upcoming big online ventures. It is appreciable way to keep your customers in engagement through the launch modes.
Apart from these things, I would recommend you to make develop a responsive website. Most of the users who are accessing online are through mobile, you might not want to lose them by keeping a non responsive website. I have recently come to know about this ready made booking software with exceptional features of popular booking websites. All that you have to do is buy the script and install it in your server. I came to know about this script through this source, Easy way to build a booking and rental platform
Source: Steven Hendrick's answer for a Quora question