You could leverage via call option LEAPs on the index of your choice. You could approach this several ways. Here are some:
(1) Use an ITM call LEAP as a 1:1 replacement for an investment in and ETF such as DIA or SPY, freeing up investment cash to deploy into your "low-fee investment funds." In terms of investment cost, for a two call LEAP 20% ITM, you'd pay a time premium under $15. That would be the cost of the reduced investment leverage if held for two years. Google "Stock Replacement Strategy" for an explanation of this concept.
(2) A variation of (1) would be to hold the two year LEAP for one year and then roll out a year back to two years out. Currently, the annual cost for that would be about $600 or 40% of the previous example.
(3) You could buy 2x the number of call LEAPs, achieving true 2x leverage. But understand that such leverage is a double sided sword. It provides a larger gain when it works and a larger loss when it fails.
(4) A way to leverage return without employing risk leverage is to utilize what is called a Repair Strategy, although in this case, you would not be using it as a repair. The idea is that if you are willing to cap your potential profit, you can obtain no cost 2:1 leverage between current price and a predetermined cap.
For example, you like the SPY. You buy 100 shares and along with a no cost one year REPAIR, you'd make $2 for every $1 the SPY rises between current price and that cap. Right now, with the SPY at $335, you could make as much as 60 points (18%) if SPY increased $30 (9%) in one year but you would make no more than that if SPY rose more than 30 points (above $365).
These are general descriptions that have more nuance than time and space allow. Also, I've left out specific details because these ideas aren't a perfect fit for all the parameters that you have laid out.
EDIT (with apologies for the length)
As requested, here's a deep dive into one of the approaches mentioned above. This one's for you @Fattie.
(4) A way to leverage return without employing risk leverage is to utilize what is called a Repair Strategy, although in this case, you would not be using it as a repair. The idea is that if you are willing to cap your potential profit, you can obtain no cost 2:1 leverage between current price and a predetermined cap.
EXAMPLE
I have modestly rounded today's quotes up/down in order to make the calculations simpler.
Buy 100 shares of SPY at $340
Buy one Apr $340 call for $23
Sell two Apr $365 calls for $11.50
The proceeds received from the two short $365 calls pays for the long $340 call. The option component (a 1x2 ratio) has a zero cost.
100 shares and a short $365 call is a covered call.
The long $340 call and the other short $365 call is a bullish vertical spread.
There are no naked options.
On an expiration basis:
Below $340 the options are worthless and you'll lose $1 for every $1 just as if you only owned the shares. A failed no cost repair has no impact on the overall position.
For every $1 that SPY is above $340, you'll make $2 ($1 from the SPY and $1 from the vertical spread.
The cap is $365 at which point you will have a gain of $25 on the SPY and $25 on the spread for a total gain of $50 (14.7%) on a $25 point up move (7.35%). This is for ~6 months so it annualizes to almost twice that.
Above $365 you make nothing more.
Dividends received are not included in these calculations.
NUANCES
There's no rule that says that the Repair must be done for zero cost. A credit is better but if you want more potential profit, you'd sell a higher strike price, resulting in a debit. Or sell a lower strike for a credit, reducing your upside. Whatever.
To evaluate these, in lieu of software, drop the option chain quotes into a spreadsheet and compare the return of different expirations as well as different strike price combinations. There are many possible Repairs so choose the one whose profit potential makes you the happiest.
Nearer expirations offer higher annual yield than further expirations.
Implied volatility affects a repair’s cost. The lower it is, the more costly the repair. If higher (for example, just before earnings), the credit will be larger, enabling you to either book the credit or use a lower long strike which will offer a higher profit potential.
Dividends inflate put premiums and deflate call premiums. This has a greater effect on options closer to the money, making a Repair less expensive (a credit). This has a greater effect on nearer expiries.
Prior to expiration, the further out the expiration, the more the options retain time premium (low theta decay) which makes subsequent adjustments (locking in gains) more difficult. For that reason, I do not care for LEAP Repairs.
Now let's dive into some position management to project some what ifs. Suppose it's five months from now and the SPY is $365. Rather than spending time doing option pricing model calculations, look at the current option chain and guesstimate future prices (the assumption is that implied volatility remains the same). Look at the 11/06/20 $315 and $340 calls which have one month until expiration. They're worth $25 and $8, respectively. See if you can figure out why these are representative of future Repair value. That means that the vertical spread has achieved $17 of its potential $25 profit.
Choices?
(1) Do nothing and hope SPY remains above $365 in order to nab the remaining $8.
(2) Close the spread and book the $17.
(3) Roll the $340 calls up, locking in some gain but reducing maximum profit.
(4) Roll the spread to 6 months out and up to say a $365/$390 vertical, giving you and additional $17 of profit potential (higher cap).
(5) Close all of the options and open say a $365/$390 Repair. You have $9 in your pocket plus the appreciation on the SPY covered call.
Such option adjustments require a higher level of option position management and would not be relevant to the buy and hold until expiration type.
There are many, many possibilities. This is just an overview for understanding the strategy.
I think that the official name for what I have described might be a covered call spread. Here's an example of where it's a true Repair for a fallen stock.
Mike drop!