solutionsbysteve

Solutions Invoice Manager is an all in one invoice management system. Create invoices for your customers and allow them to view them password protected on your site. There is also built in support for emailing customers with multiple templates including custom, payment reminders, services rendered, and more.
This plugin is free to use and comes with the GPLv2 or later license. With that said this plugin lives solely on donations. If there is no monetary value in coding this plugin than development will cease to exist. If you would like you can donate here or use the button below.
If you would like to make requests for specific features please feel free to do so at http://solutionsbysteve.com/contact/ Remember, these are simply requests and no guarantee that it will fit in to the scope of the plugin but will absolutely be taken into consideration.
Donations 
Please feel free to make feature requests with your donations. DO NOTE: these are simply requests and no guarantee that it will fit in to the scope of the plugin but will absolutely be taken into consideration. 
http://bit.ly/Donate-SolutionsInvoiceManager

Solutions Invoice Manager

Manage invoices on your very own wordpress installation. Supports emailing, PDF viewing and Reports.

Bookster

This Extra Options Addon for Bookster allows you to add extra services to your booking forms to collect additional payments from customers.
Need other features? <a href="https://wpbookster.com/downloads/all-access/" rel="nofollow ugc">Explore our All Access plan here ↗</a>
<h3>Features</h3>
<ul>
<li>Create Optional Service: Add descriptive names and images to your extra options to clearly communicate their value to customers.</li>
<li>Set Custom Pricing: Assign specific prices or additional charges to each extra option, allowing you to increase revenue or offer premium services.</li>
<li>Customize Duration: Set the duration for each extra option to accurately reflect the time required for service.</li>
<li>Targeted Assignments: Assign extras to specific services or categories, ensuring that only relevant options are presented to customers.</li>
<li>Quantity Selection: Enable customers to choose multiple extras in one go by allowing them to specify the quantity for each option.</li>
</ul>

Bookster Extra Options

This Extra Options Addon for Bookster allows you to add extra services to your booking forms to collect additional payments from customers.

Solutions Invoice Manager vs Bookster Extra Options