Investing on a budget can be profitable, too. Investors can start with just $100, a relatively small sum that can grow substantially over time when invested regularly and in the right stocks. That's especially the case for investors who buy solid dividend stocks and opt for automatic dividend reinvestment. Doing so can significantly boost market returns over the long run. With that in mind, let's look at two dividend-paying companies whose shares are trading for less than $100 right now: Gilead Sciences (GILD -0.01%) and Pfizer (PFE 0.91%). Let me explain why these two stocks are worth investing in right now. 

1. Gilead Sciences

The past three years have been an up-and-down battle for Gilead Sciences. The company ran into regulatory headwinds in the U.S. as it failed to earn approval for an important candidate, rheumatoid arthritis medicine filgotinib. Filgotinib was supposed to be Gilead Sciences' next blockbuster, so this was a blow for the company.

On the other hand, Gilead Sciences has been highly successful in the coronavirus drug market thanks to Veklury, one of the first medicines approved to treat COVID-19. Veklury helped Gilead Sciences' revenue stay afloat. And although the coronavirus drug market is shrinking as the pandemic subsides, Gilead Sciences is getting its mojo back in its most important therapeutic area: HIV. 

HIV screening, diagnosis, and treatment decreased during the early days of the pandemic, but it has been recovering. Gilead Sciences' portfolio in this area includes Biktarvy, the top-selling therapy in the U.S. market, and Descovy for PrEP, also a leader in its niche. Last year, the company also earned approval for Sunlenca, a long-acting HIV regimen, in the U.S. and Europe. This medicine will almost certainly exceed $1 billion in annual sales.

Gilead Sciences has also been making headway in the oncology market thanks to products such as Trodelvy. Although HIV remains its largest therapeutic area in revenue, and it is still developing plenty of products in this field, the biotech has been seeking to diversify away from HIV. Gilead Sciences' oncology pipeline features more than three dozen programs.

Gilead Sciences' innovation ability is a good reason it can continue delivering solid revenue and profits over the long run and rewarding shareholders through dividends. The biotech offers a yield of 3.57%, and it has raised its payouts by a solid 31.6% in the past five years. With a cash payout ratio of 44.5%, the company has plenty of room for increases. 

At the time of this writing, Gilead Sciences shares are trading for just $84.59, and at a forward price-to-earnings (P/E) of 12.4 -- compared to the average of 16.5 for the biotech industry -- Gilead Sciences' price and value both look attractive.

2. Pfizer

Pfizer's shares have substantially underperformed the S&P 500 over the past year. It is a case of the market being forward-looking: Even last year, investors were well aware that Pfizer's sales from its coronavirus products, which have allowed it to deliver record revenue, wouldn't last forever. However, the market isn't looking forward enough in my view. Pfizer has made all the right moves to plan for a world beyond coronavirus. 

The company made a series of acquisitions that helped bolster its pipeline. The latest one was that of cancer specialist Seagen for $43 billion, a move that will improve Pfizer's oncology lineup and pipeline. The drugmaker is also in the process of launching plenty of brand-new products, to the tune of roughly 19 in the next 18 months.  That will allow Pfizer's non-coronavirus revenue to grow at a good clip for years.

Further, the company should continue recording sales from Paxlovid, its COVID-19 therapy, and Comirnaty, its market-leading vaccine. The coronavirus is likely here to stay; patients at risk of developing severe cases of the illness should continue to get inoculated every year, just like they do with the flu. Although Pfizer's revenue will inevitably decline for at least a year or two due to a decline in demand for COVID-19 products, the company should return to growth eventually. 

That's why long-term investors shouldn't be worried about the company's recent poor stock market performance. In fact, that has created an excellent entry point. Pfizer's current forward P/E is 11.7. The company's shares are just $40. Pfizer's dividend yield is 4.08%, and it has raised its payouts by 20.6% in the past half-decade. Pfizer is a solid pick for both value and income-seeking investors.