I would start with thinking, am I ready and do I want to pay more than what I do now. Odd's are that the mortgage with taxes and insurance will be more than $2000. Probably about $2300 - $2500.
Also is the house worth $300,000? People can list a house for what ever they like but that does not mean that it is worth it. Are there other similar houses in the area for the same price? I like homesnap.com to look up house prices.
How is the house going to be financed. Is the seller going to hold the mortgage or do you need to find a mortgage? If you need to get a mortgage then you need to get pre-approved ASAP.
The seller can pay some of your closing costs but not all of them. You will still need to come up with a several thousand. If you have a 401k you can make a draw (without penalty but you will pay taxes) and use it for closing costs. You would need to discuss this with your 401k plan administrator.
Good luck.
