That will help out a lot.
Don't worry about the locations of the bunker. For the time being, I would set it to research as there are some items you will need at a later date.
You should have a frogger chopper. You can use that for VIP work solo and getting about in. Easy money is seeker, use the chopper, done in less than 5 mins.
Currently, biker sales are times 2. However, in true R* style, the upgrades for businesses are so expensive the return on them is minimal at low level.
Do you have a Twitch Prime account? If you have the Rainforest Prime. set up a twitch account, link it to prime, then link prime to your Social Club account and that is worth 200K a week. Easy money for nothing.
Use the Helicopter to complete the treasure hunt and Mauds bounty missions. Both give you items (Revolver and a hatchet) with lots of RP and 250K each when you complete the item tasks. Do them in the contact mission "Pier pressure" There you can run around the pier, and the beachfront killing as many people as your murderous heart desires without the cops showing up.
Make sure you spin the Casino wheel each day.
Also, do the flight school. Its good money and RP and helps bring up your stats.
If you are interested in your stats, some of them are easy to increase, just a time sink. Driving is easy, just drive on the wrong side of the road along the hard shoulder. Flight, just nick an aircraft and keep on landing it as LSA. So basically bunny hop up and down the runway. Strenth, fight people in pier pleasure mission. Walking around in stealth mode does that one. Stamina, ride a bike, run. Lung capacity. Swim under water.
Check out the GTA Online Reddit. There are loads of tips in the FAQ's and always the most efficient ways to make money.
I would avoid Doomsday Heists for the time being as they are a pain at low level with minimal vests. See if you can get some normal Heist invites. However, buy a Heavy armour combat vest. this gives you greater protection in these heists, A lot more. Only works in them though.
Oh and if you want a solo public session for whatever reason.....
Alt-tab out of GTA. Open up Resource monitor, click on the memory tab, locate the GTAV process, Right click, Suspend process for 6-7 seconds, then restart process, back to GTA. That should empty the lobby and you will be alone.. This can be helpful if the lobby is a mess and you just want to get on and do solo free roam stuff.
(starts around 0:50)