Need Sample training programs from experienced riders

An average speed of 18-20 MPH for 30 miles is not too aggressive of a 6 month expectation for many new riders, but only you know your current state of fitness.

Regarding a training schedule, starting from a low level of fitness, time spent on the bike is your first goal. Try to pedal with lower gears at a high cadence (crank RPM) of around 80+, as opposed to pushing hard on larger gears - it will save your knees and improve your overall fitness. Start with a reasonable ride time you can achieve and at the end feel winded, but not to the point of feeling sick or lightheaded. Take a day or two off each week to help your body recover. If you feel up to it, increase your time on the bike by about 10% each week. Research cycling interval training as a way to increase your fitness without spending countless hours on the bike.

Keep reading the forum and use the advanced search to dig up older posts asking questions very similar to yours.

And lastly, please don't ask the same question in different threads. People will be more apt to respond to a single thread.