I'd suggest you see you primary care doctor and tell him/her you've notice that your hair is thinning and you want to try Finasteride to stop it from proceeding any further.
Ask for a script for 5 mg Proscar. It is the commercial name for finasteride. Tell your doctor you want the 5 mg tablet of Proscar b/c that will be covered by your health insurance. Propecia (1 mg) will not be covered by insurance. Then get the 5 mg Proscar filled as a generic. That'll make it even cheaper. Mine is $4 for 90 5 mg pills. Now, cut the pill into 4 pieces and take 1/4 every day. That will last you 360 days (almost a year).
Depending on how you respond and how far your condition has progressed, you may see some regrowth in 6-12 months. About 60% of user report regrowth in that time. About 90% report that their hair has stopped falling out in that time frame.
As the OP mentioned, Rogiane 5% topical foam is a good supplement to finasteride too. If you live in an area where there is a Sams Club, you can get 120 day supply of Rogaine 5% foam for $45. I'd recommend that as well.
So for a year, you are looking at a about $150 bucks to keep your hairline. Well worth it.
I've used both finasteride and Rogaine for the past 17 years. I am in my 40s and I have a rockstar head of hair just like I did when I was in my early 20s.
Hope that helps.
Regards.