Will getting a second line run to my home from my ISP(Cable One) result in a higher speed for my home office?

Your ADSL line (the one your telecommunications company provides) has infrastructure to handle a certain bandwidth. Let's keep numbers small so you follow. let's take it in increments of 2Mbps, 4Mbps, 8Mbps, 10Mbps.

Now your line may have 10Mbps available but your ISP and internet plan only uses let's say 4Mbps. In that case you have 6Mbps available and can run a second ISP connection to the speed of say 6Mbps.

Now that you understand better let's take 2 things into consideration:

You would usually not be allowed to split the connection on the same line as most ISP's don't allow this. Thus you will need a second DSL line completely ( I am not talking about the Ethernet cable now).

Would it not be easier and cheaper to just upgrade your current ISP package? Than have 2 lines separate for work and business? That way they can still share connection but because the internet is faster now due to more bandwidth being available they can both do what they are suppose to.

So my recommendation is just increase your internet speed by upgrading your ISP package.

Staying with small numbers let's say you currently use 10Mbps but that is too slow for work and personal use to share, upgrade to 20Mbps. Instead of getting another DSL line and having another ISP account just for the same goal.

However if you are planning on large downloads/ uploads/ updates ect. it might be viable to consider the 2 line system. Very seldom will this method be the preferred choice though. 1 in a million I'd say.