I started at 60, very late, I did get my 401 to $200,000, am trying for 300,000. I think a person can live on that amount from the RMD withdrawals. $500,000 would even better, depends what you want to give up, and put in as much as the government will let you, right now over 59 1/2 is $16,500 or $3000 a month in a 401 account, Not that many people can do that but 15 to 20% of pay check is usually is good. Where I work most people put their money in the bond fund, were afraid to loose money, and didn't get very much to retire on, after 20 or even 30 years. The ones who put their money into the stock fund in 2008 and 2009 became millionaires after 10 years. I got a 30% increase in my funds one year through the stock fund, and now down about 6 1/2 percent this year. You don't loose until you move your money to the safer fund, and hopefully you get back into the market funds at a good time. 65 - 40 is 25 years, if this market goes back up like I think it will, you should have not problem. Don't be afraid to loose money, think of it as a paper loss. If you you can start a Roth that is $6000 a year the government will let you put, in equals $500 hundred a month. Find an index fund or as Buffet says to can pick 3 stocks and reinvest the dividends, favorite stocks that have been around a long time Chevron, McDonald, Coke, Pepsi, toothpaste and soap. Proctor and gamble, all these companies have been around a long time and rise their dividends every year. The index fund can produce any where from 8% percent to 12 percent per year. Wish you luck. No bills to do this, no car payment, no credit card payments, pay off the house if possible. This may sound hard, but when do you want to retire. By the way if you do this right, by booking out the 401, the 401 could make more money than you get paid at work. I have seen people do this but I didn't make it. One has to retire at some point, Buffet is doing pretty well.
