1.5% per month is conservative and achievable. You need to watch for schemes offering high returns in a very short period of time. A flashy website or high return doesn't mean a thing. In fact, those things should be warning signs more than a sense of excitement. If you are looking to get rich fast in the investing world, then you can save yourself some time and hassle by simply throwing $20 out of your car window while driving. Your end result will be the same.
The safest, predictable investment I participated in is a private investment club. There are several reasonable ones out there. Google it and look for the ones posting lower returns compared to the ones posting get-rich-quick percentages.
I can only share a brief overview of one club I participated in. This may give you some ideas of what to watch for.
The investment club I was in is private and they operate by referral only (no referral commissions, however. They just don't want to deal with people who don't understand conservative, ongoing investing.)
They only accept BTC for initial investment and they payout ROC/profits via PayPal USD. I once asked why and they said to minimize chargeback risk.
My initial investment was .0035 BTC. Payouts were made weekly in USD to my PayPal account. I think I received payments on Saturday/Sunday. They covered the PayPal fees so I received the full amount in my PayPal account. I wanted to do multiple simultaneous investments but they would only allow one at a time. According to my buddy who got me in, they reject more club members than they accept.
My payments were made for 28 weeks. The ~$2.45 per week in PayPal USD was return of capital and interest combined. Sounds like a weak return of 12.4% over 28 weeks, but I also essentially converted BTC to USD without fees or hassle.
To keep the playing field level, the minimum investment was .002 BTC and the maximum was .006 BTC. (Basically, $35-$105 USD)
In one of the three investments I've made over the past year or more, I received one unexpected bonus payout because the club investors made out big on a trade (In fairness, I didn't count that in my return calculations because it only happened once.)
They truly see it as "our" money instead of "their" money.
For disclosure: This is not a solicitation or advert. All the numbers I am listing are calculated using current BTC market rates and USD conversions. I invested in this private club successfully three times. However, I do not have a current stake in this investment club. I do have two friends who are active today (otherwise I wouldn't have even typed all this.) I do plan to invest again toward the middle of January...but right now I have holiday gifts to buy.
I can provide more details via PM because it is only for people within the US with verified US PayPal accounts only.