Yes, you can submit an offer later - assuming you don't lose the house to another buyer while you're waiting to re-submit. You should wait a month or two before re-submitting so you don't upset the seller and they reject your offer again.
1. Yes you can come back and attempt again to offer a price the seller will take.
2. It may be sold when you are ready.
3. You need to get with a good Realtor who can help you and work for you!
If you need any further help or have any questions and you don't want to post on Trulia feel free to email me.
For more information on Buyer Brokering, you can read more about the advantages and why every buyer should use one at the following http://nchomesbylarryt.wordpress.com/2011/05/15/do-i-need-a-
Best of Luck!
If the home remains available and is offered for sale to the public, you can make as many offers as you wish as often as you wish.
Please keep in mind that working through a real estate professional will greatly enhance you chances for success. Additionally, all offers should be in writing, include a deposit amount, and a "proof of funds" or "pre-approval" letter from your bank.
Knowing the trend for the local market shoul help prepare you to make a fair offer. Asking your agent to provide you with all recently sold similar homes and their sale prices may prove instrumental in presenting a successful offer.
Will you be upset if someone else comes along and buys the house for a slightly higher price?