It mainly depends on how many of you are going and what kind of houseboat you're looking for. Also, prices are different for the route and trip you want. Some are one night and one day and some are longer. There are three types of boats you could choose from, the budget class (which starts at 7k and goes up to 16k), the deluxe class (8k-18k) and the first class (12k-24k). In these, the first two have the options of AC or non AC, the first class has AC only. All three meals are also included. (These rates are for one bed room houseboats which are for two people)

You can check the package details here - http://www.holidify.com/custom-package/?referrer=utm_source%3Dwebsite%26utm_medium%3Dheader%26utm_campaign%3Dheader

Yes you can

Floating rooms which inbuilt on small boats like yachts

If you're at one with nature, Kerala is not without reason called God's own country. Its amazingly beautiful, and each moment spend will be worth it. But maybe, if you're skeptical, you can think of some other place to visit. You can refer to this list for reference - http://www.holidify.com/blog/solo-travel-india/

You can get a customized package by filling in your requirements on this link http://www.holidify.com/custom-package

For boat house how much rent

This really depends on your trip. Basic food, stay and travel (not including houseboat) would cost around INR 5,000 a day. Houseboats can be quite costly, but totally worth the price since their one of the major selling points of Alleppey.