A termsheet could in theory just be a single line like: "30% ownership at $1.5 million pre money valuation with one board seat".
But really, there is no way to respond on a Q&A site for a question that expansive since there are many, many if's and but's to cover. It'll (literally) take a book. So why not read one of the best ones on it?
Venture Deals by Brad Feld is by far the best one - I highly recommend it. It's recommended in the CA/SoCal startup circles too. It's not a very long book, written very nicely and covers everything you need to know.
Note that a termsheet is like a board full of knobs. Once you know what each knob does, you can tune it for your situation. The book will cover all that.
You'll also need valuations dollar figures. Sounds like you are pre-revenue or really early stage, so try "Scorecard valuation methodology" by Bill Payne