Obviously there are ways to increase your income, but I'm considering that outside the scope of this answer, and focusing on getting better prices.
Discounts
Some vendors will give you discounts for actions taken in the game, like Carla giving you a discount for making a sarcastic remark when you meet her. Shopping at vendors that give you a discount will help.
Raising Charisma
Much like raising intelligence for additional xp, you can raise your charisma for better prices. I keep a set of charisma gear on me, including clothes (+1-3 CHA), a hat (+1 CHA), and glasses (+1 CHA). I put these on before speaking with vendors, and it improves both buying and selling prices.
As an experiment, my character with 3 CHA sold some items without the CHA equipment (3 CHA), then I loaded and sold the same items with the equipment (7 CHA). I got approximately 200 caps without, and approximately 250 caps with.
You could also drink some alcohol first, which should pay for itself.
Perks
There's a perk for better buying and selling prices, called Cap Collector. I haven't tried this, but the exact numbers are listed on the fallout wikia.
You can also improve buying and selling prices with the perks you receive from finding Tales of Junktown Jerky Vendor magazines.
Other Items
Some specific items will give you a boost specifically to prices. Grape Mentats will give you 10% better prices and +5 Charisma for 8 minutes.
The wiki says Strong (and I have noticed that Curie and Hancock as well) likes to be out and kill things... And that gains approval even if it does not seem that way. Allow me to elaborate; you can get strong to adore/idolize you simply by going out, exploring and killing. So you do not necessarily need to do things your companion "loves" or "likes" for him to gain approval. I can confirm this is true for Curie and many people seem to agree it works for Strong too.
So my suggestion? Go to Diamond City, check the bounty board (that's left to the guy selling "swatters") and do a lot of them with him. Most bountys just requiere you to go somewhere, kill the boss of the place and loot. So do that, but remember never to lockpick.
What I am trying to say, is that the following is without logic, but still happens: I left Codsworth at Sanctuary, and you notice that he "loves" when you customize a weapon or an armor, and so I intentionally only customize things at Sanctuary to have him "loving" it, but how can it be that it took me 8 "loves" just to reach the first level of approval, and with Curie i have barely got one love and 4 likes and she is already in 3rd level of approval with my character? Well it seems that "hanging out" and "watching each other's back" raise approval silently. So you most definetelly want to take strong with you to some raider camps and gunner strongholds. He will "approve" just being there as a team teamwork. I hope someone with PC and console commands may explain how does this works (because it does) in terms of how much time spent, or xp gained, or enemies killed it takes to get "likes" equivalent approval... But that's that.
If you have trouble finding the bounty board, go to the mayor's office and ask the secretary for work. The bounty board will appear on your map after that.
Best Answer
Most of the bobbleheads are far too far away and are in strong areas. Without ridiculously careful planning and preparation, or with a rush, it would be very difficult to acquire them, and almost impossible to acquire more than one. I've made a list of the ones that are achievable easily from the start. It may also be best to leave the bobbleheads until you have acquired 10 in the Special stats, as collecting them after is (currently) the only way to raise these stats to 11:
Perception Bobblehead -
Intelligence Bobblehead -
I have made a list of why it would be difficult to obtain the others:
Strength:
Agility:
Charisma:
Luck:
Endurance:
Here's a map, showing the location of each bobblehead: